Poorly specified requirement for purchasing the meter test equipment does not help the decision maker to select the right equipment for right application. In most of cases final decision maker has little or no information on the importance of meter test equipment and how small issue could play a big role in overall testing. Meter testing activity is considered as the last and low priority activity until they dive into this sea.
This paper explains the systematic approach in selection of meter test equipment and will help to reduce the overall cost in a short term and long term.
Steps mentioned in the flow diagram will assist to reach the right selection of test equipment.
Figure 1: Process to choose the right equipment.
Various organizations, based on their meter testing objective can be broadly categorized as follows.
Various organizations, based on their meter testing objective can be broadly categorized as follows.
S.no. | Type of Organization/ department | Objectives of meters testing or Requirements |
1 | Electricity distribution company | The electricity company buys several types of meters from different meter manufacturers. They have already installed meters on network, which also vary in type, design, technology etc. Their testing objectives are as follows
v To test the meter as acceptance of purchased meter or before installation v To test the meter returned from field for maintenance or calibration after certain interval v Sample testing for evaluation of tender v To test the meter on site v To comply with regulatory requirements |
2 | Independent Test laboratory or test houses or National physical Laboratories | These kinds of organizations have to test various type of meters, hence equipment need to be versatile and flexible to test all new generation of meters. |
3 | Meter Manufacturer | The main objective for meter manufacturer is to achieve greater scale of economies in production, thus their requirement will be considering
v Complete process time, speed of testing v Multitasking at one bench means same bench can be used for calibration, adjustment, programming and performing other functions v Automation in testing to reduce the manpower requirements and achieve Quality in testing v Fulfil regulatory requirement like IEC /ISO etc. |
4 | OEMS or Big industries, | Mostly they test small number of meters; hence either portable or single position test bench will be preferable. |
5 | Service provider | Newly emerged segment from decision of electric utilities to outsource the meter testing activity. Their requirement can be for onsite testing or laboratory testing, depending on their service contract with utilities. |
Table 1: Type of Organisation and their requirements
Different objective of meter testing leads to direction of major group of meter test equipment.
S.no. | What you want to do? | Meter test equipment |
1 | To test the meter in bulk | Stationary meter test equipment e.g. 10, 20 40 position meter test bench
OR Meter Test bench (Gantry system) OR specially designed test system to achieve high productivity |
2 | To test the meter in a small quantity e.g. sample testing in laboratory | Stationary meter test bench e.g. Single position meter test bench |
3 | To test the meter on site | Portable meter test equipment |
Table 2:Define objectives and selection of meter test equipment
Category of meter testing can be divided mainly into two categories. One is suitable for testing in laboratory and another is suitable for onsite testing. Onsite test equipment should be lightweight equipment.
On site testing is done by two different methods: –
It is important for bulk meter tester that test equipment is: –
It is recommended to pay attention on the production flow process, time required by each activity and total time require in one lot of tested meter.
If equipment is going to use simply for routine testing, then features related to type testing such as Harmonic generation, frequency variation etc become less significant.
Small quantity testers are generally research laboratories of a manufacturer or test house or OEMs, that tests several different kinds of meters; hence test equipment for such user should be able to perform special tests or type tests like 3rd, 5th and other higher harmonics, frequency, and other influence quantity tests.
Mainly Accuracy of meters is tested by sensing of rotor mark in electromechanical meter and LED blinking in Electronic meter. These kinds of testing need sensing device, which should be able to sense both (rotor mark as well LED blinking). Sensing device or so-called “Scanning head” should be able to sense the optic pulse; criteria of such pulses are defined in IEC 62052-11 clause 5.11.1 and 5.11.2. Some meters also give electrical pulse output as defined in IEC 62053-31 and to test these pulses will require an additional compatible adopter according to output type A or B.
S.no | Name of test & Details | How to test | What is required |
1 | Accuracy test of electromechanical meter | By sensing the rotor mark | Scanning head and Error calculation system |
2 | Accuracy test of electronic meter | By sensing optical pulse output “LED Blinking | Scanning head and Error calculation system |
3 | Accuracy test of electronic meter | By counting electrical pulse | Pulse adopter and Error calculation system
Note: – Please define here type of pulse output and operating voltage or just simple relay contact |
4 | Accuracy test of electronic meter, which doesn’t give neither LED blinking nor electrical pulse output | Same like dial test or register test | Perform just like dial test, value of initial and final reading can be entered either manually or by reading meter via infrared scanning head if meter support IEC 1107 protocol.
This method required much time and higher uncertainty, which has made it less preferable |
5 | Register test or Dial test in electromechanical meter | Energy recorded by the meter under test compared with energy delivered by the | Test bench should have provision to control the current precisely after completion of set energy. Software should have facility to enter the initial & final value of energy register and finally calculate the % error of meter under test |
6 | Register test or Dial test in electronic meter | Energy recorded by the meter under test compared with energy delivered by the | v Test bench should have provision to precisely control the current after completion of set energy.
v Reading of meter via Infrared scanning head as per IEC 1107. It is recommended to discuss detailed about the communication. |
7 | Other tests as per IEC standards | As mentioned in IEC standards | Hardware and software capability of test bench |
8 | Functional test and other special test like testing of load profile, communication RS232, RS485, MBUS, PLC | As defined by manufacturer or tester | Test system should be equipped with hardware and software point of view to perform specific test |
Table 3 : Meter technology and testing methods
The tests which need to be performed by different user group vary due to difference in their meter testing objectives. This information guides you on essential and non-essential feature of test equipment. For example equipment used for routine testing doesn’t need to have harmonic (3rd, 5th, sub, odd & even) generation and other type testing features.
S.no. | User & Location | Name of test | What is required |
1 | Electricity company (Laboratory) | v Accuracy test
v Starting current v Creep Test v Register test v Functional test |
Test bench |
2 | Electricity company (Laboratory sample testing) | v Same as above
v Additional type testing like influence quantity test |
Test bench capable to perform additional type testing |
3 | Electricity company (onsite testing) | v Accuracy test
v Register test and testing of different tariff registers v Connection check and analysis |
Portable equipment with vectorial analysis tools to identify the connection check |
4 | Manufacturer (Production | v High voltage testing
v Calibration and adjustment v Accuracy test v Starting current v Creep Test v Register test v Functional test v Software/ Firmware programming |
Insulation voltage test
Test bench capable to perform additionally function test and capable to communicate with meter to programme the meter |
5 | Manufacturer’s (R&D Laboratory | Type testing | Test bench should be capable to perform the type test and conduct special test in the presence of exotic waveform |
Table 4: Test to be performed
Although each country has its own regulatory requirements, which are drawn from, national or international standards but in general following factor influences the decision of meter test equipment.
It is recommended to use high precision measuring equipment to cover all kind of accuracy class meters economically, and this serve following other purpose
Automatic meter test benches are better fitted into the other regulatory requirements as defined in the international standard IEC 62052-11
S.no. | Accuracy class of meter under test | Recommended Accuracy of meter test equipment |
1 | Electromechanical meter class 1&2 | Class 0.1 or 0.2 |
2 | Electronic meters class 0.5 | Class 0.05 |
3 | Electronic meter class 0.2 | Class 0.02 |
Table 5:Accuracy class of meter V/s Accuracy of meter test equipment
User needs to review the available type meter on network and also consider future trends in meter technology, then decide about the accuracy and other parameters of meter test equipment
After completion of study, user needs to make market search on the available equipment, solutions, understanding the features & functions of the new technologies, cost involvement and upgradeability for future.
Finally define your technical requirement and proceed for purchase action.
Analyze the available offers in details or go for demonstration to answer your queries.
In Europe, it is quite common to discuss very concrete and in detailed, information on the type of meter and how test will be performed. Technical information on meter type can be given to supplier, so that tester gets very concrete and clear answer on possibilities from test equipment suppliers.
Here mentioned few tips can be helpful to define the specification of meter test equipment. Product category mentioned here is most preferred, by different user groups.
Apart from general technical requirements and features mentioned above, following characteristics need to be specially taken care.
Portable meter test equipment comprises reference meter and electronic source to generate the test parameters and conduct the testing. Below mentioned few points are important to consider while selecting the testing.
Metering technology is changing at faster speed. To cope with this speed needs extra care in selection of meter test equipment, particularly test bench. Adequate information on meters and their technology, test to be performed & methodology, metrology involved in the testing and available meter test equipment technology will help tester to choose the right equipment which can meet not only present requirements but futuristic also.
If electronic meters are need to be tested using IEC 62056 communication, please mentioned the details of such requirement.
Although metering standard defined 10VA per phase for normal electronic meter, but in case of additional accessories in the meter, addition VA may be allowed. Current drawn by the SMPS power supply of some electronic meter can distort the waveform quality and this could affect the overall measurement uncertainty of test system.
Total resistance of current circuit which include cable, contact type and resistance of current circuit of meter is the key factor in deciding the total VA rating of current circuit of the source.
Traceability is a unbroken chain of measurement relationship between national standard and standards used in test system
In direct connected meters, a link between voltage and current circuit, which cannot be open during testing. To test such meter needs single phase multi-secondary voltage transformer (MSVT) for single phase meters, and isolating current transformer (ICT) for testing of three phase meters. The test bench, which has ICT, is capable to test single phase closed link meters.