 
  
 
 
Regulation for Installation and Maintenance 
of Metering Systems  
 
 
 
 
Authority for Public Services Regulation  
 
 
17 August  2020  
 
 
 
 
 
     
 ii Installation and Maintenance of Metering Systems  v 0.3  CONTENTS  
  Page  
1. Introduction  ................................ ................................ ................................ ..........  1 
1.1 Purpose  ................................ ................................ ................................ ...............  1 
1.2 Scope ................................ ................................ ................................ ...................  1 
1.3 Interpretation  ................................ ................................ ................................ ........  1 
1.4 Definitions  ................................ ................................ ................................ ............  2 
2. Use of Approved Meters ................................ ................................ .......................  6 
2.1 Conf ormity Assessment  ................................ ................................ .......................  6 
2.2 Responsibilities of Network Operators and Suppliers  ................................ ...........  6 
2.3 Meter Markings and Information Requirements  ................................ ....................  7 
2.4 Upgrading of Software  ................................ ................................ .........................  8 
2.4.1  Protection for Legally Relevant Software  ................................ ..............................  8 
2.4.2  Availability of Software Upgrades  ................................ ................................ .........  8 
2.4.3  Approval to Upgrade  ................................ ................................ ............................  9 
2.5 Determination of Verification Life  ................................ ................................ ......... 10 
2.5.1  Initial Verification Lives  ................................ ................................ ........................ 10 
2.5.2  Extension of Verification Life  ................................ ................................ ............... 10 
2.5.3  Regulatory review of Verification Lives  ................................ ................................ 12 
3. Meter Verification, Acceptance and Calibration Requirements  ............................ 12 
3.1 Requirements for Approved Laboratories  ................................ ............................ 12 
4. Acceptance of Meters  ................................ ................................ ......................... 13    
 iii Installation and Maintenance of Metering Systems  v 0.3  4.1.2  Visual Inspection of New Meters at Acceptance  ................................ .................. 15 
5. Calibration and Verification  ................................ ................................ ................. 15 
5.1 Calibration requirements  ................................ ................................ ..................... 15 
5.2 Calibration and Verification of New Meters  ................................ .......................... 15 
5.3 Calibration and Verification of Meters after Repair  ................................ .............. 16 
5.3.2  Visual Inspection of Meters at Verification following Repair  ................................ .16 
6. Verification Tests  ................................ ................................ ................................ 17 
6.1.1  Refere nce Conditions for Tests  ................................ ................................ ........... 17 
6.1.2  Verification Tests to be Undertaken  ................................ ................................ ....19 
7. Sealing of Meters for Verification  ................................ ................................ ......... 23 
7.1.2  Form of Crimped Security Seal  ................................ ................................ ........... 24 
7.1.3  Control of Sealing Tools  ................................ ................................ ...................... 24 
7.2 Sealing of Meter Terminations  ................................ ................................ ............ 25 
7.2.1  Equipment to be Sealed  ................................ ................................ ...................... 25 
7.2.2  Type of Seal  ................................ ................................ ................................ ........ 26 
8. On Site Cal ibration  ................................ ................................ .............................. 26 
8.1.1  Calibration requirements  ................................ ................................ ..................... 26 
8.1.2  On-site Calibration Equipment  ................................ ................................ ............ 27 
8.2 Routine On -site Calibration Checks  ................................ ................................ ....29 
9. Overall Metering System Accuracy Requirements  ................................ .............. 30 
10. Commissioning of CT Operated Metering Installations  ................................ ........ 32 
Schedule 1 – Approved List of Approved Conformity Assessment Laboratories …….………. 34    
 ii Installation and Maintenance of Metering Systems  v 0.3       
 1 Installation and Maintenance of Metering Systems  v 0.3  1. Introduction  
1.1 Purpose  
The purpose of th is Metering Regulation  is to establish the requirements for metering 
equipment which shall be installed at all connections between networks of all licenced 
distribution companies and all network user s. 
1.2 Scope  
This Regulation  applies  to all Metering Equipment owned by the Network User  and/or the 
Network Operator  for the provision of an electricity connection at the premises of a Network 
User and the financial settlement for  electricity trans ferred . Where appropriate, it shall also 
apply to the transfer of electrical energy generated by the Network User  and supplied to the 
network of the Network Operator . 
This Regulation  applies to all connections made to the networks owned or operated by  all 
Licensed Network Operators in the Sultanate of Oman.  
1.3 Interpretation  
In addition to special meanings contained in the Definitions that follow , within this document:  
• References to the masculine shall include the feminine and references in the 
singular shall include references in the plural and vice versa,  
• Except where explicitly stated otherwise all references to section shall be a 
reference to a section in this document , 
• All clock times or other references to time, shall refer to the standard time in the 
Sultanate of Oman , which is four hours in advance of Universal Time Co -ordinated 
(UTC),  
• Any reference to a law or regulation shall be a reference to that law or regulation 
applicable in the Sultanate of Oman  or, following the replacement of that law or 
regula tion the new law or regulation from the date it comes into force , 
• Any general reference to a standard shall be a reference to the current version of 
that standard from its date of implementation . A reference to a particular 
requirement in a standard shall be a specific reference to that requirement in the 
referenced version of the standard unless a later version of the standard has an 
equivalent requirement in which case it shall be a reference to that equivalent 
requirement in the current version of the st andard.  
    
 2 Installation and Maintenance of Metering Systems  v 0.3  1.4 Definitions  
For the purpose of these Regulations, the following definitions which, where appropriate , have 
been taken from the International Electrotechnical Vocabulary as defined in IEC 60050 apply  
unless an alternative definition has been used in the IEC Standards specified in section 2.1.1.2 . 
In that case, the definition used in that IEC Standard  shall also apply to the relevant section of 
this Regulation : 
Sector Law  - means Royal Decree 78/2004 as amended by Royal Dec ree 59/2009,  Royal 
Decree 47/2013  and 78/2020 . 
MoCIIP -  means the Ministry of Commerce, Industry and Investment Promotion  
APSR  – means the Authority for Public Services Regulation  
Accredited Laboratory  – means a testing facility accredited to ISO/IEC 17025.  
Approved Conformity Assessment Laboratory – means a laboratory independent of 
meter manufacturers, meter suppliers and/or meter owners that hold s current accreditation 
certificates issued by  an agency or agencies recognised by MoCIIP  - demonstrating 
compliance with the appropriate requirements of ISO/IEC 17065:2012 and ISO/IEC 
17025:2017  and, having satisfied MoCIIP  - of its ability in respect of conducting Conformity 
Assessments of electricity metering equipment is approved by MoCIIP  - for this purpose.  
Approved Laboratory – means a testing facility located in Oman that is either an 
Accredited Laboratory that has been recognised by MoCIIP  or a laboratory approved by 
MoCIIP  to undertake meter testing activities.  
Base - (of an energy mete r) means the back of the case by which it is generally fixed and 
to which are attached the measuring element, the terminals or the terminal block, and the 
cover  
Note – For a flush -mounted meter, the meter base can include the sides of the 
case.  [IEV 314 -07-14] 
Basic Current (Ib)– means the value of current in accordance with which the relevant 
performance of a direct connected meter is fixed . [IEV 314 -07-06] 
Case  - (of an energy meter) means the set that comprises the base and the cover. [IEV 
314-07-17]    
 3 Installation and Maintenance of Metering Systems  v 0.3  Check Meter  – means a meter of the same class as the Main Meter but its function is to 
support the Main Meter readings in the event of its failure or large errors exceeding the 
limits specified.  
Conformity Assessment  – means the demonstration that specifie d requirements relating 
to a meter  are fulfilled.  
Cover - (of an energy meter) means the enclosure on the front of the meter, made either 
wholly of transparent material or of opaque material provided with window(s) through which 
the operation indicator (if  fitted) and the display can be read.  [IEV 314 -07-16] 
Current Transformer – means an instrument transformer in which the secondary current, 
in normal conditions of use, is substantially proportional to the primary current and differs 
in phase from it by an  angle which is approximately zero for an appropriate direction of the 
connections  [IEV 321-02-01] 
Customer  – means any person, corporate body, or company who has a connection or 
supply agreement with a Network  Operator  for the provision of electricity.  
Display - (for static meters) means a device which displays the content(s) of (a) 
memory(ies) . [IEV 314 -07-11] 
Distribution Company  – means an entity holding a licence to distribute or distribute and 
supply electricity issued pursuant to the Sector Law . 
Indo or Meter  – means a meter which can only be used in areas offering additional 
protection against environmental influences (e.g. in a house or in a cabinet) . [IEV 314 -07-
20] 
Interval Data  – meter data collected at defined intervals  for energy settlement or billing 
purposes . 
Main Meter  – means the primary Meter used for billing purposes . 
Maximum Current (Imax)– means the highest value of current at which a meter meets the 
specified accuracy requirements  as specified by the manufactur er.  
Meter Type  – means a particular design of meter, manufactured by one manufacturer, 
having:  
a) similar metrological properties;     
 4 Installation and Maintenance of Metering Systems  v 0.3  b) the same uniform construction of parts determining these properties;  
c) the same ratio of the maximum current to the refe rence current  
Note 1 – The type may have several values of reference current and reference 
voltage.  
Note 2 – Meters are designated by the manufacturer by one or more groups of 
letters or numbers, or a combination of letters and numbers. Each type has one 
designation only.  
Note 3 – The type is represented by the sample meter(s) intended for the type test s 
and whose characteristics (reference current and reference voltage) are chosen 
from the values given in the tables proposed by the manufacturer. [IEV 314 -07-07] 
(Meter) Constant – means  the value expressing the relation between the active energy 
register ed by a meter and the corresponding value of the test output.  
Note – If this value is a number of pulses, the constant should be either pulses per 
kilowatt -hour (imp/kWh) or watt -hours per pulse (Wh/imp) [IEV 314 -07-08] 
Memory  - (for static meters) means the element which stores the digital information 
representing the measured energy. [IEV 314 -07-10] 
Minimum Current ( Imin) – means the  lowest value of current at which the meter is specified 
by the manufacturer to meet the accur acy requirements  
Network operator  – means an entity holding a licence to transmit and/or distribute 
electricity issued pursuant to the Sector Law    
Network User – is a generic term that includes customers, generators and other network 
operators using a net work of a licenced network operator . 
Operation Indicator  - means a device which gives a visible signal of the operation of the 
meter.  [IEV 314 -07-13] 
Rated Current  (In) – means value of current in accordance with which the relevant 
performance of a transf ormer operated meter is fixed . [IEV 314 -07-02] 
Reference Frequency  – means the value of the frequency in accordance with which the 
relevant performance of a meter is fixed . [IEV 314 -07-05]    
 5 Installation and Maintenance of Metering Systems  v 0.3  Reference Voltage  – means the value of the voltage in accordance with which the relevant 
performance of a meter is fixed . [IEV 314 -07-04] 
Register - means an electromechanical or electronic device which stores and displays the 
information representing the measured energy  
Note 1 – In static meters, the register comprises both memory and display.  
Note 2 – A single display may be used with multiple electronic memories to form 
multiple registers.   [IEV 314 -07-09] 
Socket  - (of an energy meter) means a base with jaws to receive  the terminals of a 
detachable meter and which has terminals for connection to the supply line  
Note – The socket can be intended to receive one or several meters. [IEV 314 -07-
15] 
Terminal Block  – means the support made of insulating material on which all or some of 
the terminals of the meter are grouped together. [IEV 314 -07-18] 
Terminal Cover – means the cover which protects the meter terminals and, generally, the 
ends of the external wires or cables connected to the terminals  [IEV 314 -07-19] 
Test Output Device  - (of an energy meter) means a device which can be used for 
determining the meter error.  
Note – This device can be, for electromechanical induction meters, a mark on the 
disk, where the passage of the mark is detected by an external photoelectric device, 
or, for static meters, an internal electronic pulse emitting device. [IEV 314 -07-12] 
Transitional Current ( Itr) – means the value of current at and above which the meter is 
specified by the manufacturer to lie within the smallest maximum permissibl e error 
corresponding to the accuracy class of the meter  
Verification  – means the process whereby a meter, following manufacture or 
refurbishment, is tested in an Accredited Laboratory, prior to installation, and is 
demonstrated to meet the accuracy requirements of th is Technical Standard . 
Verification Life  – means the peri od which a Meter used for billing purposes can remain 
in service without being laboratory tested. This period is defined for each type of Meter and 
is based upon ongoing sample testing.     
 6 Installation and Maintenance of Metering Systems  v 0.3  Year  – means a calendar year according to the Gregorian calendar.  
2. Use of Approved Meters   
2.1 Conformity Assessment  
No natural or legal person shall permit the introduction of a meter to the market in the 
Sultanate of Oman unless that meter is of a type that appears on the list of  approved meters 
maintained by the Ministry of Co mmerce, Industry and Investment Promotion (MoCIIP ).  
2.1.1.1  For a meter to be included in the list of approved meters, an acceptable conformity 
assessment certificate must be provided  from an Approved Conformity Assessment 
Laboratory , demonstrating that the meter  meets the requirements of relevant IEC 
Standards as amended by this Regulation and Technical Standard s issued by 
MoCIIP . In the absence of any instruction to the contrary, the conformity 
assessment test shall be undertaken in accordance with the requireme nts of IEC 
62052 -11:2016.  
2.1.1.2  In the context of section 2.1.1.1 , relevant IEC Standards, include:  
a) IEC 62052 -11 – Electricity metering equipment (AC) – General requirements, 
tests and test conditions - Part 11: Metering equipment;  
b) IEC 62053 -21 - Electricity metering equipment (AC) - Particular requirements - 
Part 21: Static meters for active energy (classes 1 and 2);  
c) IEC 62053 -23 - Electricity metering equipment (AC) - Particular requirements - 
Part 23: Static meters for reactive energy (classes 2 and 3); and  
d) IEC 62052 -31 - Electricity metering equipment (AC) - General requirements, 
tests and test conditions - Part 31: Product safety requirements and tests.  
Togeth er with those sections of other IEC Standards to which specific mention is made in these 
standards1. 
2.2 Responsibilities of Network Operator s and Suppliers  
2.2.1.1  No network operator  or supplier shall permit a new connection to be made to its 
network using a meter o f a type that is not on the approved list  and/or for which a 
Verification certificate has not been provided . Where a meter has been approved 
                                                
1 For example, in section 5.2.2.2 of IEC 62052 -11:2016 it is required that the shock test be undertaken 
in accordance with the requirements of IEC 60068 -2-27 and the basis for the environmental conditions 
specification in IEC 62052 -31:2015 is IEC 61010 -1:2010.    
 7 Installation and Maintenance of Metering Systems  v 0.3  at the time of its installation but that approval has subsequently been withdrawn  
other than by virtue of the verif ication period expiring , the transmission or 
distribution operator to whose network the relevant connection is made shall ensure 
the replacement of that meter within a maximum period of two years unless 
otherwise instructed by  the MoCIIP . 
2.2.1.2  Where a meter  is otherwise discovered in use that is not of a type on the approved 
list, or is an approved meter but does not meet the accuracy class requirements for 
the capacity of the connection , the relevant network operator shall arrange its 
replacement by an appropri ate meter of an approved type within a maximum period 
of one week following its discovery unless otherwise directed by MoCIIP .  
2.2.1.3  The network operator  shall ensure that the installed meter is of a type that permits 
the correct billing of the requested tariff  and shall maintain the meter installation in 
a fully operational and verified condition until such time as the connection is 
removed.  
2.2.1.4  The network operator  shall ensure that all passwords which permit access to meter 
data and parameter settings have been changed from manufacturer’s default 
passwords prior to energising the connection.  
2.2.1.5  Following energisation of a new connection, the network operator shall assume 
responsibility for the ongoing of the maintenance of the meter and all network 
equipment:  
 On the network side of the outgoing terminals of a direct connection meter;  
 On the network side of the demarcation isolator which shall normally be on 
the network  user’s side of the measurement CTs in the event of CT 
connected meters.  
  
2.3 Meter Markings  and Information Requirements  
2.3.1.1  The meter manufacturer or supplier shall comply with the information requirements 
of section 5.12 of IEC 62052 -11, section 5 of IEC 62052 -31 with the clarifications 
stated in this section 2.3  regarding markings and information declared optional in 
section 5 of IEC 62052 -31 and the meter purchase contract regarding optional 
markings and information.     
 8 Installation and Maintenance of Metering Systems  v 0.3  2.3.1.2  The designation of function shall be included on either the case marking or the 
display.  
2.3.1.3  The IP rating shall be shown on the meter case.  
2.3.1.4  The case and display markings shall be indelible, distinct and le gible from outside 
the meter. Symbols shall be at least 2.75 mm high. Text shall be at least 1.5 mm 
high and contrast in colour with the background with a preference for black lettering 
on a white background.  
2.3.1.5  The markings of meters intended  for outdoor lo cations shall withstand solar 
radiation. Multiple values of Unom and ƒnom may be marked if so  specified by the 
manufacturer  and an appropriate conformity assessment certificate has been 
obtained . 
2.3.1.6  The serial number shall be provided in a position  where it i s not readily 
disassociated from parts determining the metrological characteristics.   
2.3.1.7  The language for all text included in meter case and display markings shall be 
English with all hazard warning details repeated in Arabic  
2.4 Upgrading of Software  
2.4.1  Protectio n for Legally Relevant Software  
2.4.1.1  Meters supplied to the market in Oman shall be fitted with a sealable setting 
(physical switch, software upgrade socket, secured parameter or other approved 
arrangement) that prevents the upgrading of legally relevant softw are without 
breaking the calibration seal.  
2.4.1.2  All modifications to legally relevant software shall be considered as a repair after 
which the meter will be submitted for verification testing in accordance with the 
requirements of section 5.3. 
2.4.2  Availability of Software Upgrades  
2.4.2.1  The supplier of any meter into the market in Oman shall arrange that the meter 
manufacturer provides secured updates of all legally relevant software and/or other 
software to MoCIIP  together with either:  
 an application for approval of the meter with the up dated software installed;     
 9 Installation and Maintenance of Metering Systems  v 0.3   details of the already approved meter designation with the updated software 
installed.   
2.4.2.2  Where the software upgrade affects the legally relevant software, an application for 
approval of the meter shall be accompanied with an appropriate conformity 
assessment which may include sections relating to the unchanged physical 
capability, functionalit y and parameters that have been submitted as part of the 
previous approval. Only those sections that relate to the changes being introduced 
by the upgrade require repeat testing.   
2.4.3  Approval to Upgrade  
2.4.3.1  MoCIIP  shall consider the impact of the installation o f this software and issue such 
instructions as are appropriate. Where the software does not affect legal metrology 
and does not conflict with any aspect of functionality that is required in Oman, there 
shall be a presumption that installation is appropriat e. Based on the nature of the 
proposed upgrade to non -legally relevant software, MoCIIP  shall determine 
whether the upgrade:  
a) Can be carried out on meters currently installed without verification being 
necessary;  
b) Must be carried out on all meters or only th ose meters where there is another 
requirement for this upgrade to be installed; and  
c) Where installation is required on all meters, the period of time after which 
full installation must have taken place.  
2.4.3.2  Where the software upgrade affects the legally releva nt software MoCIIP  shall 
determine whether the upgrade:  
a) Must be carried out on all meters or only those meters where there is another 
requirement for this upgrade to be installed; and   
b) Where installation is required on all meters, the period of time after which 
full installation  or the removal from service of all affected meters  must have 
taken place . 
2.4.3.3  Details of all changes to installed software shall be recorded in a separate event 
log. 
2.4.3.4  Where MoCIIP  issues an instruction for the upgrade of any meter softwa re, no 
person shall prevent its installation, or the replacement of the meter to permit 
installation as part of a repair, being carried out at any reasonable time.     
 10 Installation and Maintenance of Metering Systems  v 0.3  2.5 Determination of Verification Life  
2.5.1  Initial Verification Lives  
2.5.1.1  As part of the approval proc ess, MoCIIP  shall assign a verification life to each new 
meter approved for use in Oman. Unless an application for approval is 
accompanied by an appropriate assessment of reliability according to an 
internationally recognised procedure that indicates a lon ger verification life would 
be appropriate, the verification life assigned to a meter as part of the approval 
process shall be no more than 10 years.  
2.5.1.2  MoCIIP  will approve the acceptability of internationally recognised procedures for 
reliability assessment of electronic equipment as being relevant for application to 
meters at its sole discretion.  
2.5.1.3  Unless the verification life is extended in accordance with the requirements of 
section 2.5.2  or section 2.5.3 , the meter shall be removed from service at the end 
of this initial verification life.  
2.5.2  Extension of Verification Life  
2.5.2.1  At le ast 3 years prior to the end of verification life of a particular meter type, the 
person responsible for its maintenance may apply to MoCIIP  for the verification life 
to be extended. The applicant shall provide details of the number of meters in 
service, t heir age and the number of that meter type that has been replaced 
because of defect by year of manufacture.  
2.5.2.2  MoCIIP  shall seek information from all parties that would be affected by such an 
extension in verification life on the number of meters for which th ey are responsible 
of that manufacture and type by year of manufacture and verification.  
2.5.2.3  MoCIIP  shall create a sampling plan and instruct the affected parties to remove a 
sufficient number of meters from service, approximately in proportion to the number 
for which they are responsible, as will form a homogenous sample. Sufficient 
additional meters shall be included to allow for the number of rejections permitted 
by section 8.3 and table 1 in Annex 2 of OIML Guide  G 20 for the Surveillance of 
utility meters  in service on the basis of sampling inspections . 
2.5.2.4  For a population of meters to be considered homogeneous, they shall have the 
same characteristics, namely:  
 Manufacturer     
 11 Installation and Maintenance of Metering Systems  v 0.3   Type or model  
 Capacity/rating  
 Year of manufacture  
 Number of the conformity assessment certificate  
 Number of registers (unless multi –rate versions share approval 
characteristics and are metrologically equivalent)   
 The dates of the last verification may differ at most by 1 year.  
2.5.2.5  Where necessary, up to 5 years’ meter installations will be comb ined to form a 
single sample. The earliest installed meters shall be the group tested.  
2.5.2.6  The meters that are provided as part of the sample shall be inspected and tested 
at an approved or accredited laboratory or approved or accredited laboratories 
designate d by MoCIIP  to test the sample or parts of the sample. The designated 
laboratory or laboratories may be operated by an affected party or parties but shall 
be independent from the meter manufacturer and any meter supplier providing 
meters manufactured by th e manufacturer. The inspection and test of the sample 
shall be the same as that required for initial verification.  The tests undertaken shall 
be the verification tests specified in section 6. 
2.5.2.7  The parties providing meters as part of the sample shall be permitted to count this 
provision as part of their routine calibration requirement.  
2.5.2.8  The results shall be collated and analysed by MoCIIP . 
2.5.2.9  Following submission of the test data to MoCIIP , the designated laboratory or 
laboratories shall retain the meters that formed the sample tested for a period of 3 
months to allow MoCIIP  to request further testing if necessary. At the end of this 
period, th ey shall be returned to the providing party.  
2.5.2.10  In the event that the test indicates that there is not a case for extending the 
verification life of the meter type, all parties responsible for maintenance of that type 
of meter shall ensure their removal from service at the end of the initial verification 
period.  
2.5.2.11   In the event that the test indicates that it would be reasonable to extend the 
verification life of the meter, MoCIIP  shall revise the record of verification lives 
accordingly. MoCIIP  shall define an y maintenance or component replacement that 
may be required to permit extension of the verification life. The replacement of a    
 12 Installation and Maintenance of Metering Systems  v 0.3  battery by a battery of the same type shall not be considered as a component 
replacement provided it is not necessary to replace a verification seal.  
2.5.2.12  Nothing shall prevent a person responsible for maintenance of electricity meters 
from requesting a further extension to the verification life of meters of a type for 
which it is responsible.  
2.5.2.13  It shall be for MoCIIP  as its sole right to  determine whether it is likely to be in the 
best interests of electricity consumers to proceed with any part of the sampling 
process.  
2.5.2.14   Except where MoCIIP  contracts with a designated laboratory that is not part of the 
electricity sector, the parties invo lved in the process shall be responsible for their 
own costs.  In the event that MoCIIP  contracts with a designated laboratory that is 
not part of the electricity sector, that laboratory’s costs shall be met by the person 
or organisation requesting a change  to the verification life.  
2.5.3    Regulatory review of Verification Lives  
2.5.3.1  Where APSR  considers that it may be in the best interests of electricity consumers 
to consider whether it may be reasonable to extend the verification life of any 
particular meter type, i t shall be entitled to commence the extension process 
outlined in section 2.5.2  by making application to MoCIIP . 
3. Meter Verification , Acceptance  and Calibration Req uirements  
3.1 Requirements for Approved Laboratories  
3.1.1.1  Approved Laboratories must satisfy MoCIIP  that they are capable of accurately 
undertaking acceptance and verification testing as outlined in sections 4 and 5 but 
do not require to be accredited to ISO/IEC 17025 . MoCIIP  shall:  
 formally approve all laboratories in this category;  
 investigate the operation of an approved laboratory where there is a 
suspicion of non -compliance with the necessary requirements;  
 issue improvement notices to the operator of an approved laboratory where 
necessary;  
 remove the status of approved laborator y where appropriate.     
 13 Installation and Maintenance of Metering Systems  v 0.3  3.1.1.2  An approved laboratory which is subject to an improvement notice shall not conduct 
any activity specified in the improvement notice until such time as MoCIIP  has 
formally stated that the issue that was the subject of the improvement notice has 
been resolved. In the event that MoCIIP  removes approval of a laboratory, the 
operator shall immediately cease all acceptance, verification and routine calibration 
activity that relied on the use of that laboratory.  
3.1.1.3  To ensure traceability to international standards, all equipment used by Approved 
Laboratories to undertake acceptance and/or verification testing  shall be calibrated 
annually  by an ISO 17025 accredited calib ration laboratory  and all standards used 
shall be maintained in a temperature -controlled dust -free environment at all times. 
A copy of the calibration certificate issued by the accredited calibration laboratory 
plus a copy of its current accreditation cert ificate shall be provided to the MoCIIP  
prior to the next use of the relevant equipment. Any test carried out using any 
equipment after the expiry date shown on its calibration certificate registered with 
MoCIIP  or more than one year after the date of issu e of that certificate, whichever 
is the earlier, shall be void.  
3.1.1.4  It is accepted that approved laboratories may not keep all equipment used for 
testing energised at all times. However, before undertaking any acceptance or 
verification testing, all equipment required to complete that test shall have been 
energised for a minimum period of 2 hours.     
4. Acceptance of Meters  
4.1.1.1  Prior to meters being accepted into Oman, an acceptance test shall be carried out 
on behalf of the distribution company. This acceptance test  shall normally be 
carried out by an Approved Laboratory but may be undertaken in an Accredited 
Laboratory outside Oman provided that the purchaser submits proof of 
Accreditation , obtains the approval of MoCIIP  and all tests are witnessed by a 
suitably qua lified representative of the purchaser. Prior to undertaking the electrical 
verification tests, a visual inspection as outlined in section 4.1.2  shall be 
undertaken . 
4.1.1.2  The form of the acceptance test shall be a visual inspection as specified in section 
4.1.2  followed by an electrical test that shall the same as a Verification te st as 
defined by IEC 62058 -31:2008  and detailed in section 6. Where the batch of meters 
being introduced is less than 40, all Meters shall be tested.     
 14 Installation and Maintenance of Metering Systems  v 0.3  4.1.1.3  Where more tha n 40 Meters are being introduced, acceptance testing may be 
carried out on a statistical basis:  
 If the batch does not exceed 100 meters, 5% of that batch should be 
sampled and tested. If 2 or more meters are out of specification, the batch 
shall be  rejecte d. If only 1 meter is non-conforming , another sample may be 
tested. In this second sample every meter sh all be within specification for 
the batch to be accepted.  
 For batches  of more than 100 meters , the minimum number of meters to be 
tested shall be 40. For a batch size less than 1000 the purchaser may 
specify one of the sample sizes in Table 4. If only 1 meter more than the 
maximum number specified in  Table 4 is non-conforming , another sample 
may be tested. In this second sample , the maximum number of meters  shall 
be as spec ified in Table 4 for the batch to be accepted.  
 For batches of 1000 or more the purchaser shall ensure that the batch is 
split into sub -batches of no more than 1000 me ters and may specify one of 
the sample sizes for each 1000 Meters as shown in Table 1. The maximum 
number of non -conforming meters that are found in the sample for the 
remainder of the batch of 1000 meters or sub-batch  where there are more 
than 1000 meters to be accepted are also shown in Table 1.  
Table 1 - Statistical Testing for a batch of 1000 Meters  
Number of Meters tested  40 70 100 1000  
Maximum number of non -conforming meters  0 1 2 10 
 
4.1.1.4  Samples shall be randomly taken from the batch or sub -batch of Meters. The 
sampler shall ensure that they are taken from all parts of the batch or sub -batch 
and represent the batch  or sub -batch  as a whole.  
4.1.1.5  In all cases, any Meter found to be non -conforming  shall be rejected even if the 
remainder of the batch of which it was a part is accepted.  
4.1.1.6  A test certificate recording the test results for the meters tested and recording 
details of all other meters that are part of the batch or sub -batch shall be provid ed 
to the purchaser.     
 15 Installation and Maintenance of Metering Systems  v 0.3  4.1.2  Visual Inspection of New Meters at Acceptance  
4.1.2.1  Visual Inspection of new meters at Verification and acceptance shall include an 
inspection that confirms:  
a) Calibration seals are in place and intact;  
b) The Meter has not suffered any damage and has no parts missing;  
c) The meter markings specified in section 2.3 are complete.  
5. Calibration and Verification  
5.1 Calibration requirements  
5.1.1.1  Meters sh all be subjected to verification testing prior to first installation  and, where 
reinstallation following the expiry of its verification life is permitted, prior to such re -
installation.  
5.1.1.2  Meters shall be replaced or re -verified following refurbishment at the  end of their 
verification lives as established in accordance with the requirements of section 2.5.  
5.1.1.3  Verification tests shall always be undertaken by an accredited laboratory or an 
approved laboratory.  
5.2 Calibration and Verification of New Meters  
5.2.1.1  Following manufacture, all meters shall be sealed and subjected to calibration and 
Verification in an Accredited Laboratory or Approved Laboratory according to the 
requirements of IEC 62058 -31:2008  for individual Verification and the calibration 
requirements specified in section 6. Statistical Verification is not permitted.  Prior to 
Verification the Meter shall be sealed in accordance with the requirements of 
section 7. Prior to undertaking the electrical verification t ests, a visual inspection as 
outlined in section 5.2.1.4  shall be undertaken.  
5.2.1.2  A Verification certificate, signed by the individual responsible for the test, shall be  
issued by the Accredited Laboratory or Approved Laboratory for each Meter that 
successfully passes Verification testing. This certificate may be in the form of an 
individual certificate for each Meter or a certificate recording the details of all Meters 
that passed Verification and were included in a batch tested together. The 
certificate must be provided by the Accredited Laboratory or Approved Laboratory 
to the party submitting the meter for test .    
 16 Installation and Maintenance of Metering Systems  v 0.3  5.2.1.3  The month and year of the Verification shall be indelibly  marked on the Meter Case 
prior to the meter being returned to the party submitting the meter for test .  
5.2.1.4  Visual Inspection of new meters at Verification shall include an inspection that 
confirms:  
a) Calibration seals are in place and intact;  
b) The Meter has not  suffered any damage and has no parts missing;  
c) The meter markings specified in section 2.3 are complete.  
5.3 Calibration and Verification of Meters afte r Repair  
5.3.1.1  Following repair, all meters shall be sealed and subjected to calibration and 
Verification in an Accredited Laboratory or an Approved Laboratory according to 
the requirements of IEC 62058 -31:2008  for individual Verification and the 
calibration re quirements specified in section 6. Statistical Verification is not 
permitted.  Prior to Verification the Meter shall be sealed in accordance with the 
requirements of section 7. Prior to undertaking  the electrical verification tests, a 
visual inspection as outlined in section 5.3.2  shall be undertaken  
5.3.1.2  A Verification certificate, signed by the individual respon sible for the test, shall be 
issued by the Accredited Laboratory or Approved Laboratory for each Meter that 
successfully passes Verification testing. This certificate may be in the form of an 
individual certificate for each Meter or a certificate recording  the details of all Meters 
that passed Verification and were included in a batch tested together. The 
certificate must be provided by the Accredited Laboratory or Approved Laboratory 
to the party submitting the meter for test . 
5.3.1.3  The month and year of the Ver ification shall be indelibly marked on the Meter Case 
prior to the meter being returned to the party submitting the meter for test .  
5.3.2  Visual Inspection of Meters at Verification following Repair  
5.3.2.1  Visual Inspection of meters at Verification following repair  shall include an 
inspection that confirms:  
a) Calibration seals are in place and intact;  
b) The Meter has not suffered any damage and has no parts missing;  
c) If the year of manufacture is 2020 or later, that the meter markings specified in section 
2.3 are complete; or, if the year of manufacture is 2019 or earlier, that, at minimum the 
meter markings that exist include:     
 17 Installation and Maintenance of Metering Systems  v 0.3  • Manufacturer’s Name  
• Unom 
• Imax 
• Ibase 
• Serial number  
• Numbe r of phases  
• Number of wires  
• Register multiplier (if other than unity)  
• Meter constant(s)  
• Year of manufacture  
• Accuracy class  
• Directionality of energy flow if the meter is bidirectional or unidirectional. (No 
marking is required if the meter is capable only o f positive direction energy flow.)  
• Meter type  
• fnom 
• Environmental Class  
• The connection mode(s) for which the Meter is specified and for which approval 
has been given by MoCIIP  
• Connection terminals uniquely identified to distinguish between terminals.  
 
6. Verif ication Tests  
6.1.1  Reference Conditions for Tests  
6.1.1.1  Before calibration, it should be confirmed that the requirements as specified in 
Table 2 are fulfilled. This table contains the requirements for ambient temperature, 
warming up of the equipment and the permissible error of the power source used 
for the calibration.  
Table 2 - Reference Conditions for Verification Tests  
Influence quantity  Reference Value  Permissible tolerances for meters of 
class  
0.2S 0.5S 1 2 
Ambient Temperature  23 oC ± 2 oC 
Voltage  Unom ± 1.0%    
 18 Installation and Maintenance of Metering Systems  v 0.3  Influence quantity  Reference Value  Permissible tolerances for meters of 
class  
0.2S 0.5S 1 2 
Frequency  ƒnom ± 0.3% ± 0.3% ± 0.3% ± 0.5% 
Phase Sequence  L1 – L2 – L3 - 
Voltage unbalance  Zero - 
Waveform  Sinusoidal voltages 
and currents  Distortion  
< 2.0% < 2.0% < 2.0% < 3.0% 
Continuous magnetic induction  of 
external origin  Zero - 
Magnetic induction of external origin at 
the reference fnom Zero Induction value that causes a variation of 
error not greater than  
± 0.1% ± 0.1% ± 0.2% ± 0.3% 
but should be<0.05 mT  
Electromagnetic RF fields           30 kHz 
to 6 GHz Zero < 1 V/m  
Equipment warm -up period prior to 
testing   > 2 hours  
Current  Current range of 
device under test  1% 1% 2% 2% 
Power factor  Power factor range of 
device under test  Current to voltage phase difference ± 2o  
 
6.1.1.2  Before calibration  of polyphase meters , it should also be confirmed that the voltage 
and current balance requirements as specified in Table 3 are fulfilled.  
Table 3 - Voltage and current balance for polyphase meters  
Condition  Class of Meter  
0.2S 0.5S 1 2 
Each of the voltages between phase and neutral and between any two 
phases shall not differ from the average corresponding voltage by more 
than ± 1%     
 19 Installation and Maintenance of Metering Systems  v 0.3  Condition  Class of Meter  
0.2S 0.5S 1 2 
Each of the currents in the conductors shall not differ from the average 
current by more than  ± 1% ± 2% 
The phase displacements of each of these currents from the 
corresponding phase -to-neutral voltage, irrespective of the phase angle, 
shall not differ from each other by more than  2o 
 
6.1.2  Verification Tests to be Undertaken  
6.1.2.1  The minimum tests to be undertaken prior to issuing a verification certificate or 
installation approval certificate shall be conducted in the following order:  
a) AC voltage test  
b) No Load Test  
c) Starting Load Test  
d) Accuracy Tests  
e) Register Test  
Where a meter is intended for use as a bidirectional meter, the starting load 
test, accuracy tests and register test shall be repeated for currents in the reverse 
direction.  
Where the meter is to be certified  for multiple values of Unom, the no load test, 
starting load test, accuracy tests shall be carried out at the lowest and highest 
values of Unom. 
Prior to tests being undertaken, the meters shall be energised at Unom and 
loaded with a current at unity power factor of 0.1Ib for direct connected meters 
or 0.1In for transformer connected meters  to reach thermal stability.  
6.1.2.2  These tests shall be conducted as detailed:  
a) AC Voltage Test – Test number 1  
 
A test voltage that shall be substantially sinusoi dal, having a frequency between 
45 Hz and 65 Hz, and be applied for 2 s. The power source shall be capable of 
supplying at least 500 VA. The rise time and the fall time of the test voltage shall 
be ≤ 2 s. The auxiliary circuits with reference voltage equal  to or below 40 V    
 20 Installation and Maintenance of Metering Systems  v 0.3  shall be connected to earth. During this test, no flashover, disruptive discharge 
or puncture shall occur.  
In the case of meters of insulation class I the rms test voltage applied shall be 
1.6 kV. In the case of meters of insulation class  II the rms test voltage applied 
shall be 3.2 kV.  
 
b) No Load Test – Test number 2  
 
The no load test to be undertaken shall be in accordance with the requirements 
of section 5.4 of IEC 62058 -31. 
 
c)   Starting Current Test – Test number 3  
 
When the meter is ener gised at the reference voltage (and, in the case of 
polyphase meters, with balanced load) and connected as shown in its diagram 
of connections, a meter for which a basic current is specified shall start and 
continue to register at the current given in Table 4. 
 
Table 4 - Value of current for starting current test  
Meter Connection  Class of Meter  Power 
Factor  0.2S 0.5S 1 2 
Direct Connection  - - 0.004 Ib 0.005 Ib 1 
CT Operated  0.001 In 0.001 In 0.002 In 0.003 In 1 
 
Where a starting current Ist is specified, the meter shall be started at unity power 
factor and 1.5 t allowed for the first pulse to occur and a further 1.5 t allowed for 
the second pulse to occur. The effective time between the pulses should be 
determined and it shown that a third pulse occurs in the same time period. The 
objective of the test is to prove that the meter starts and continues to operate at 
the s pecified Ist. 
 
The expected time t between pulses is:  
 
3.6 x 106 
m.k.Unom.Ist 
    
 21 Installation and Maintenance of Metering Systems  v 0.3  where:  
k is the number of pulses emitted by the meter per kWh  
m is the number of elements  
 
d) Accuracy Tests  
 
Accuracy tests shall be carried out for single phase meters for which a value of 
Ib is specified and polyphase meters for which a value of In is specified at the 
test points specified in Table 5. Tests shall be undertaken in the order specified 
without waiting for thermal equilibrium to be attained between the 
measurements.  
Table 5 – Accuracy test points and p ercentage error limits  
Test  Value of current for  
Power 
factor  Meter 
type Load (for 
polyphase 
metes)  Limits or percentage error for 
meters of class  
Direct 
connected 
meters  Transformer 
connected 
meters  0.2S 0.5S 1 2 
4 0.05 Ib 0.01 In 
1 Single 
and 
polyphase  Balanced  ± 1.0 ± 0.4   
0.02 In   ± 2.5 ± 1.5 
5 Ib In 1 Single 
and 
polyphase  Balanced  ± 0.2 ± 0.5 ± 1.0 ± 2.0 
6 Ib In 0.5 lag  Single 
and 
polyphase  Balanced  ± 0.3 ± 0.6 ± 1.0 ± 2.0 
7 Ib In 1 Polyphase  Single 
phase  ± 0.3 ± 0.6 ± 2.0 ± 3.0 
8 Ib In 1 Polyphase  Single 
phase  ± 0.3 ± 0.6 ± 2.0 ± 3.0 
9 Imax Imax 1 Single 
and 
polyphase  Balanced  ± 0.2 ± 0.5 ± 1.0 ± 2.0 
    
 22 Installation and Maintenance of Metering Systems  v 0.3  Test 7 shall be undertaken with the meter supplied with three phase 
symmetrical voltage. The current shall be applied to any of the phases.  
Test 8 shall be undertaken with the meter supplied with three phase 
symmetrical voltage. The current shall be applied to a  different phase from that 
in test 7. 
Where meters are designed to measure bidirectional flows, tests shall be 
carried out with current in each direction sequentially.  
Where a meter is stated to measure flows in one direction only, a test shall be 
carried  out at unity power factor with reversed current flow at each of Ib and Imax 
to demonstrate that no measurement takes place.  
 
Where  the manufacturer has defined values for Imin, Itr and Imax, rather than Ib or In and 
Imax , accuracy tests shall be carried out at the test points detailed in Table 6 at Unom 
instead of the tests specified in Table 5.  
Table 6 - Accuracy test points and percentage error limits  
Test  Value of current  Power 
factor  Meter 
type Load (for 
polyphase 
metes)  Limits or percentage error for 
meters of class  
0.2S 0.5S 1 2 
4 Imin ≤ I < Itr 1 Single 
and 
polyphase  Balanced  ± 0.4 ± 1.0 ± 1.5 ± 2.5 
5 Itr ≤ I < Imax 1 Single 
and 
polyphase  Balanced  ± 0.2 ± 0.5 ± 1.0 ± 2.0 
6 Itr ≤ I < Imax 0.5 lag  Single 
and 
polyphase  Balanced  ± 0.3 ± 0.6 ± 1.5 ± 2.5 
7 Itr ≤ I < Imax 0.8 
lead Single 
and 
Polyphase  Balanced  ± 0.3 ± 0.6 ± 1.5 Test 
5 
result 
± 2.5 
8 Imax 1 Single 
and 
polyphase  Balanced  ± 0.2 ± 0.5 ± 1.0 ± 2.0 
 Change from tests 5 and 6     
 23 Installation and Maintenance of Metering Systems  v 0.3  Test  Value of current  Power 
factor  Meter 
type Load (for 
polyphase 
metes)  Limits or percentage error for 
meters of class  
0.2S 0.5S 1 2 
9 
Itr ≤ I < Imax 1 
Polyphase  Single 
phase  ± 0.3 ± 0.7 ± 1.0 ± 1.5* 
10 0.5 lag ± 0.5 ± 1.0 ± 1.5 ± 2.5* 
11 
Itr ≤ I < Imax 1 
Polyphase  Single 
phase  ± 0.3 ± 0.7 ± 1.0 ± 1.5* 
12 0.5 lag  ± 0.5 ± 1.0 ± 1.5 ± 2.5* 
 
Tests 9 and 10 shall be undertaken with the meter supplied with three phase 
symmetrical voltage. The current shall be applied to any of the phases.  
Tests 11 and 12 shall be undertaken with the meter supplied with three phase 
symmetrical voltage. The current shall be applied to a different phase from that 
in tests 9 and 10.  
* in these tests. the error shift for cl ass 2 meters may be greater than these 
values provided the overall error remains within ± 2.5%  
Where meters are designed to measure bidirectional flows, tests shall be 
carried out with current in each direction sequentially. Where a meter is stated 
to measure flows in one direction only, a test shall be carried out at unity power 
factor with reverse d current flow at each of Imin and Imax to demonstrate that no 
measurement takes place.  
 
e) Register Test  
This test shall be performed by measuring a sufficient amount of energy to verify 
that the accuracy of incrementing the register reading is better than ±1.0%.  The 
test shall be done for each meter on at least one tariff register.  
7. Sealing of Meters for Verification  
7.1.1.1  All Meters shall be sealed prior to Verification. The sealing may be undertaken by:  
a) the use of a one -piece case which cannot be opened; or  
b) the use of a crimped security seal  as specified in section 7.1.2 .      
 24 Installation and Maintenance of Metering Systems  v 0.3  7.1.2  Form of Crimped Security Seal  
7.1.2.1  A seal shall be comprised of two parts – a short p iece of wire rope and a sealing 
ferrule - which, when fitted together and compressed by a sealing tool, will prevent 
the removal of a seal without clear evidence of that removal. The following 
specification for the seal is intended to ensure that it cannot  reasonably be 
accidentally broken or removed.  
7.1.2.2  The wire rope shall be 150mm long, have a minimum diameter of 0.9mm, have a 
breaking load of at least 880N and be manufactured from 7 strands of zinc coated 
steel wire.  
7.1.2.3  The sealing ferrule shall be a tin plate d, annealed copper ferrule between 5.0 and 
6.0mm in length with an internal diameter between 1.95 and 2.25mm, an external 
diameter between 4.0 and 4.6mm and be constructed such that at no point the wall 
of the ferrule is less than 0.8mm thick.  
7.1.2.4  The sealing tool will comprise a compression tool and compression dies such that 
the tool will compress the ferrule onto the wire rope so that the formed seal will 
withstand a minimum tensile load of 200N. The compression dies shall be designed 
to mark the compressed ferrule on two opposing sides:  
 On one side with an identifying mark or up to 3 alphanumeric characters as 
approved by MoCIIP  uniquely identifying the Accredited Laboratory, and  
 On the other side with 3 alphanumeric characters that will uniquely identify t he 
operative who has fitted the seal.  
7.1.3  Control of Sealing Tools  
7.1.3.1  Sealing tools must be provided by the Accredited Laboratory for each operative 
authorised to remove and replace verification seals. The Accredited Laboratory 
shall provide facilities for the operative to store the sealing tool in a secure location 
to which only that operative has access when it is not in use. The owners of the 
Accredited Laboratory shall ensure that a senior member of their staff examines all 
sealing tools each month and maint ains a signed record detailing the presence (or 
otherwise) of the tool and its condition.  
7.1.3.2  Compression dies must not be used by more than one operative but may be 
transferred between operatives provided two operatives do not use the same tool 
in the same m onth. No Accredited Laboratory shall hold duplicate sets of dies.    
 25 Installation and Maintenance of Metering Systems  v 0.3  Where an operative will no longer seal Meters tested on behalf of the Accredited 
Laboratory, the Accredited Laboratory must immediately recover the compression 
dies issued to that operative.   
7.1.3.3  Compression dies that no longer make legible marks must not be used and must 
be immediately destroyed by the Accredited Laboratory. The Accredited Laboratory 
may arrange that a replacement set of dies with the same identifier are 
manufactured and issued to the operative or alternatively issue a replacement 
sealing tool with a different identifier to the operative at its choice.  
7.1.3.4  The Accredited Laboratory shall keep a record of when a sealing tool is issued to 
an operative or sent for repair. For dies in u se, this record shall show:  
 The identification mark of each set of dies held,  
 The name or the person to whom the dies were issued or the person or 
company to whom they have been sent for repair,  
 The dates of issue and return  
7.1.3.5  For dies destroyed this record shall show the date and reason for their destruction.  
7.1.3.6  For dies that have been lost or stolen, a record shall be kept showing the date and 
location of loss. The Accredited Laboratory shall immediately advise MoCIIP  and 
all affected meter purchasers the deta ils of all meters that are marked as having 
successfully passed Verification tests during the month in which the loss occurred .  
7.1.3.7  All records kept in accordance with sections 7.1.3.4  to 7.1.3.6  shall be retained for 
a period of 10 years following the destruction or loss of the dies and shall be made 
available to MoCIIP  on request.  
7.1.3.8  On being given reasonable notice, the Accredited Lab oratory shall produce any 
dies for inspection by MoCIIP  or their agent on request. In this respect, the agency 
retained by the Accredited Authority to undertake their accreditation review should 
be considered as an agent of MoCIIP . 
7.2 Sealing of Meter Termina tions  
7.2.1  Equipment to be Sealed  
7.2.1.1  To ensure that the accuracy of the measurement displayed by the metering 
equipment is maintained, t ermination seals shall be applied to provide an indication 
of access having been taken to any part of the metering system or immediate    
 26 Installation and Maintenance of Metering Systems  v 0.3  network area.  It is acknowledged that, where indicative seals are used, their 
removal does not constitute proof of tampering and that the removal of any 
termination seal may indicate that legitimate work has been undertaken.  
7.2.1.2  Seals shall be applied to the following locations and any other  locations where it 
may be possible to  access equipment in a manner that could result in an incorrect 
measurement being ma de: 
 All meter terminal block covers;  
 All covers protecting communications modules associated with the metering 
system;  
 All cut -out fuse units and terminations and MCCB terminations associated 
with LV supplies;  
 All VT secondary fuses associated with the me tering system;  
 All termination blocks on which any CT or VT secondary wiring is 
terminated;  
 All test block covers; and 
 All withdrawable VT units.  
7.2.2  Type of Seal  
7.2.2.1  Tamper evident security seals as specified and provided by the relevant network 
operator and approved by the Authority for Public Services  Regulation, Oman shall 
be used to seal all terminations.   
8. On Site Calibration  
8.1.1  Calibration requirements  
8.1.1.1  Meters shall be replaced or re -verified following refurbishment at the end of their 
verification lives as established in accordance with the requirements of section 2.5. 
Verification tests shall always be undertaken by an accredited laboratory or an 
approved laboratory.   
8.1.1.2  The person responsible for maintenance of metering systems shall undertake 
intermediate calibration checks on metering systems as detailed in Table 7. These 
checks may be carried out in an approved laboratory or on -site provided    
 27 Installation and Maintenance of Metering Systems  v 0.3  appropriate test equipment is used. If any metering equipment is removed from site 
or replaced , a full recommiss ioning test shall be conducted on the reconnected 
metering installation.   
Table 7 – Routine On site Calibration Requirements for Metering Installations  
Connection 
Capacity  Installation Type  On Site Calibration Required  
≤ 1MVA  Direct  None  
CT Operated  Every 5 years  
> 1MVA - 5 MVA   Every 5 years  
> 5 MVA  Main and Check Meters of 
Same Type  Every 5 years  
Main and Check Meters of 
Different Type  None  
 
8.1.1.3  Verification seals shall not be removed during an on -site calibration check. If a 
verifica tion seal is removed at an approved laboratory, a full verification test shall 
be carried out following its replacement.  
8.1.1.4  Calibration checks will also be undertaken wi thin 2 business days of:  
a) Any cumulative register not recording the same value as the sum of the values 
recorded in the relevant interval registers for any day;  
b) The values recorded by main and check meters differing by more than 1.5 times 
the limit of error in Table 9  
8.1.2  On-site Calibration Equipment  
8.1.2.1  Equipment used for on -site c alibration shall be portable meter test equipment 
capable of delivering a measurement uncertainty within the values shown in Table 
8. 
    
 28 Installation and Maintenance of Metering Systems  v 0.3  Table 8 - Measurement uncertainty for equipment used to test active energy meters on site  
Maximum overall uncertainty of calibration 
equipment  Class of meter under test  
0.2S 0.5S 1 2 
Measurement at unity power factor  ±0.06%  ±0.1%  ±0.4%  ±0.4%  
Measurement at other than unity power factor  ±0.12%  ±0.2%  ±0.6%  ±0.6%  
 
8.1.2.2  Equipment used for on -site calibration testing shall be verified by an accredited 
laboratory annually and a copy of the certificate issued shall be provided to the 
MoCIIP  prior to its next use. Any t est carried out using any equipment after the 
expiry date shown on its calibration certificate registered with MoCIIP  or more than 
one year after the date of issue of that certificate, whichever is the earlier, shall be 
void.  
8.1.2.3  Equipment used for on -site cal ibration testing shall be confirmed by an approved 
laboratory at least every three months and records kept of these tests although a 
formal certificate need not be issued.  
8.1.2.4  Such a three -monthly test may be carried out by simultaneously calibrating the 
same three phase kWh meter using the meter test bench of the approved laboratory 
and the portable test equipment. In this case the difference between the error of the 
reference meter as determined by the test bench and that determined by the mobile 
testing stat ion is to be considered as the error of the on -site test equipment. The 
accuracy of the reference meter shall not be considered relevant as it is only an 
intermediate instrument that has no bearing on the result of the reference 
measurement.  
8.1.2.5  If it is not possible to simultaneously measure the reference kWh -meter (with the 
optical scanning heads of both the test bench and the on -site test equipment 
scanning the led output) as described in section 8.1.2.4 , the measurements must 
be performed in direct succession. As the stability of the reference kWh -meter is 
important for this sequential test, class 0.2S kWh -meter shall be used as the 
reference meter.  
8.1.2.6  The requirements  for the reference measurements for tests as described in 
sections 8.1.2.4  and 8.1.2.5  are:     
 29 Installation and Maintenance of Metering Systems  v 0.3  - difference error ('bench error' minus 'mobile error') < 0 .3 %  
- change in subsequent error measurements < 0 .1 % 
8.1.2.7  At least once per month, the on -site test equipment shall be used to carry  out an 
on-site calibration test on the same three -phase kWh meter and a record kept of 
these monthly tests. Where the change in subsequent error measurements is 
>0.2%, all onsite tests carried out since the previous monthly test shall be 
considered void a nd the equipment returned to an approved laboratory for 
investigation. A network operator may conduct this calibration test more frequently 
than once per month, in which case the test considered void will be those since the 
last test where the error was wi thin the prescribed limit.  
8.1.2.8  When conducting the tests outlined in sections 8.1.2.4  to 8.1.2.7  the equipment 
must always be tested with the current clamps used for its annual verific ation which 
shall also be used when conducting all on -site tests.  
8.1.2.9  A copy of the test record for each test described in sections 8.1.2.4  to 8.1.2.7  shall 
be provided to MoCIIP  or APSR  on request.  
8.1.2.10  Equipment used for on -site calibration testing shall be stored and transported using 
a proprietary aluminium or steel transport cas e with rigid foam protection designed 
to accommodate each article.    
8.2 Routine On -site Calibration Checks  
8.2.1.1  An on -site calibration check shall include at minimum:  
a) A visual check without removing covers that confirms:  
i. The current transformers are of the corre ct ratio and polarity and 
correctly located to record the required power flow;  
ii. (Where fitted) the voltage transformers are of the correct ratio and 
polarity and correctly located to record the required power flow;  
iii. The meters are set to the same current tra nsformer and voltage 
transformer ratios as the installed measurement transformers;  
iv. The meters have the correct compensation for errors in the 
measurement transformers/connections and losses in power 
transformers where appropriate;   
v. The cabling is such that  the burdens on the measurement transformers 
will be within the correct limits;     
 30 Installation and Maintenance of Metering Systems  v 0.3  vi. All of the appropriate calibration seals and terminal cover seals are in 
place , noting that t erminal cover seals are required at all locations where 
the CT and/or VT cabling is  terminated and on all VT fuses. The 
identification marks on these seals shall be recorded as part of the 
programme  for all on -site calibration checks.  
b) A test programme that demonstrates:  
i. The relationships between voltages and currents are correct and that  
phase rotation is standard at the meter terminals;  
ii. The metering equipment detects phase failure and operates the 
required remote alarms and/or local indications as appropriate;  
iii. The output of the metering system correctly records the energy in the 
primary system at the connection point. This test programme shall 
include a  series of at least three accuracy tests of different duration  
including one that is of sufficient duration to cause the cumulative 
energy register to advance. Where a metering installation  records power 
flows in both directions, the on-site calibration c heck shall prove active 
energy flows in both directions and (at minimum) reactive flows in one 
direction are being accurately displayed . 
c) Where remote reading of the meter data via a communications link is proposed, the 
on-site calibration test shall include a comparison of each register data with that 
recorded by the remote reading system for the same period. The relevant network 
operator s hall ensure that the appointed data collector provides the necessary 
assistance and information to allow this confirmation check to be undertaken.  
8.2.1.2  It is anticipated that routine on -site calibration tests shall make use of such 
reasonable load flows as are  possible with confirmation being demonstrated that 
the metering equipment is recording such flows accurately. Where such tests are 
not conclusive additional testing may be required including testing and an 
Accredited Laboratory or Approved Laboratory as d etailed in section 6. 
9. Overall Metering System Accuracy Requirements  
9.1.1.1  The c ombined maximum permissible errors for metering installations shall be as 
recorded in Table 9.    
 31 Installation and Maintenance of Metering Systems  v 0.3  Table 9 – Combined Maximum Permissible Errors for each Connection Capacity  
Conditi on Limits of error  at stated  Power Factor for Active  Power 
and Energy measu rement 
Current  expressed  as a 
percentage  of rated 
measuring  current Power 
Factor  Limits of error  for Connecti ons 
>100  
MVA  >20–100 
MVA  >1–20 
MVA  <=1 
MVA  
120% to 10% inclusive 1 ±0.5%  ±1.0% ±1.5%  ±1.5% 
Below 10% to 5% 1 ±0.7%  ±1.5%  ±2.0%  ±2.5% 
Below 5% to 1% 1 ±1.5%  ±2.5%    
120% to 10% inclusive 0.5 lag ±1.0%  ±2.0%  ±2.5%  ±2.5% 
120% to 10% inclusive 0.8 lead ±1.0%  ±2.0%  ±2.5%  ±2.5% 
Conditi on Limits  of error for Reactive  Power and Energy at stated  
Power Factor  
Current  expressed  as a 
percentage  of rated 
measuring  current Power 
Factor  Limits of error  for Connecti ons 
>100  
MVA  >20–100 
MVA  >1–20 
MVA  <=1 
MVA  
120% to 10% inclusive 0 ±4.0%  ±4.0% ±4.0%  ±4.0% 
120% to 20% inclusive 0.866  lag ±5.0%  ±5.0%  ±5.0%  ±5.0% 
120% to 20% inclusive 0.866  lead ±5.0%  ±5.0%  ±5.0%  ±5.0% 
 
9.1.1.2  To ensure that this is achieved, the accuracy classes of metering equipment 
installed shall be as shown in Table 10. 
Table 10 - Accuracy Classes by Connection Capacity for Metering Installation Components  
Connection 
Capacity  Active 
Power and 
Energy 
Meters  Reactive  
Power and 
Energy 
Meters  Current 
Transformer  No of 
Secondary 
Windings  Voltage 
Transformer  No of 
Secondary 
Windings  
≤ 1MVA  2 2 0.5 1 1 - 
> 1MVA - 5 MVA  1 2 0.5 1 1 1 
> 5 MVA - 20 MVA  1 2 0.5 2 1 2 
> 20 MVA – 100 MVA  0.5S 2 0.2S 2 0.5 2 
> 100 MVA  0.2S 2 0.2S 2 0.2 2 
    
 32 Installation and Maintenance of Metering Systems  v 0.3  10. Commissioning of CT Operated Metering Installations  
10.1.1.1  Where CTs and/or VTs are mounted in equipment under the control of the network 
operator, the network operator shall be responsible for ensuring that the appropriate 
commissioning tests are undertaken. In all other circumstances, the person 
providing and in stalling the equipment shall be the person responsible for 
commissioning the metering system.  
10.1.1.2  At the time CT operated metering systems are installed, the person responsible for 
installation shall undertake a commissioning test to confirm the installation is 
correctly installed and sealed . 
10.1.1.3  This check shall include:  
a) Tests that demonstrate that:  
i. The current transformers are of the correct ratio and polarity and 
correctly located to record the required power flow;  
ii. (Where fitted) the voltage transformers are o f the correct ratio and 
polarity and correctly located to record the required power flow;  
iii. The relationships between voltages and currents are correct and that 
phase rotation is standard at the meter terminals;  
iv. The burdens on the measurement transformers ar e within the correct 
limits;  
v. The meters are set to the same current transformer and voltage 
transformer ratios as the installed measurement transformers;  
vi. The meters have the correct compensation for errors in the 
measurement transformers/connections and losses in power 
transformers where appropriate;  
vii. The output of the metering system correctly records the energy in the 
primary system at the connection point;  
viii. The metering equipment detects phase failure and operates the 
required remote alarms and/or local indications as appropriate;  
ix. An accuracy test of the complete metering system as soon as the 
installation is energised and supplying load.  Where a metering 
installation records power flows in both directions, the post 
commissioning check shall prove active  energy flows in both directions 
and (at minimum) reactive flows in one direction are being accurately 
displayed . 
b) A visual inspection that confirms of all of the appropriate calibration seals and terminal 
cover seals are in place. Terminal cover seals are required at all locations where the    
 33 Installation and Maintenance of Metering Systems  v 0.3  CT and/or VT cabling is terminated and on all VT fuses. The identification marks on 
these seals shall be recorded as part of the commissioning programme.  
c) Where remote reading of the meter data via a communications link is proposed, the 
commissioning test shall include a comparison of each register data with that recorded 
by the remote reading system for the same period. The relevant network operator shall 
ensure that the appointed data collector provides the necessary as sistance and 
information to the person responsible for commissioning.  
10.1.1.4  A copy of the commissioning details shall be provided to the network operator and 
the network user by the person responsible for them being undertaken.  
 
     
 34 Installation and Maintenance of Metering Systems  v 0.3  Schedule 1 – Approved List of Approved Conformity Assessment Laboratories  
 
As a starting point, the list could include those laboratories approved in EU for this work, 
defined as “Notified Bodies” in the list available at:  
http://ec.europa.eu/growth/tools -
databases/nando/index.cfm?fuseaction=directive.pdf&refe_cd=2014%2F32%2FEU&requestt
imeout=900  
This is a complete list for all measuring instrume nts and it would be necessary to extract those 
approved for assessing Active Electrical Energy Meters (Annex V MI -003). 
 
Should MoCIIP  wish to create its own list from scratch, a possible mechanism for assessing 
laboratories is available at https://www.oiml.org/en/oiml -cs/oiml -issuing -authorities . 
 
 
 
 
 
 
 
 
 
 
 
[End of Document]  