By Y. K. Nama

ZERA1:4_2007

Figure 1 - Test equipment supplied in Enel project

This scenario has brought significant changes in meter manufacturing and management. Today utilities are playing an active role from the design of the meter to the quality control process. It has been observed that meter testing is among the least discussed topics of mass scale manufacturing of energy meters, in spite of its importance and the need to meet regulatory requirements.

CHALLENGES
Managing the mass scale testing of newly manufactured energy meters is a challenging task for production managers. The main challenges are in the areas of:

  • Synchronisation and automation of various test stages
  • Optimisation of process flow and reduction of the idle time of meters
  • Automation and effective management of tests that need to be performed to meet the IEC and other regulatory requirements. Accuracy testing has become tougher and more costly due to the shunt meter
  • Special functional testing to ensure the proper working of components of meters like circuit breaker, communication test, pulse output test, etc.
  • Data administration, with the data generated at each test stage necessary for monitoring, analysis and administration, and the need for data storage for traceability and further evaluation purposes, etc.

TEST SYSTEMS FOR MASS MANUFACTURING
Modern meters are not simply a cash counter but have a number of value added features and functionality such as connection/disconnection, communications, etc. Generally the following tests and tasks are performed before shipping of meters:

  • High voltage testing
  • Adjustment/calibration of meter
  • Accuracy and other tests as per applicable standards
  • Downloading the necessary firmware and tariffs into the meter
  • Testing of special functions, including
    • Pulse input/output
    • Circuit breaker (connection and disconnection)
    • Communication modem.
ZERA2:4_2007

Figure 2 - Mobile gantry-type test system

The test solution provider for mass testing of meters needs to have knowledge of meters, metrology and meter testing, and project and process management, enabling quick development with a short reaction time. Various types of test solutions are available to meet the aforesaid challenges of mass manufacturing. The design of a test system and level of automation mainly depends on the following factors:

  • Volume of meter production (current and future targets)
  • Number of tests, function tests and sequences to be performed
  • Available space and process flow
  • Availability of skilled labour
  • Labour cost in a particular country vs cost of test system
  • Availability of funds and Return on Investment period.

ZERA offers several test solutions to manufacturers as well as utilities to manage mass testing effectively. These test systems can be classified as follows.

CELLULAR TEST SYSTEM
This type of test system is designed to perform a defined set of tests/tasks as a stand-alone unit. The operator needs to move the meter under test from one place to another and to connect the meter at each test system. Defined tests are performed automatically. Approval or rejection of a meter under test is based on set criteria. Data collected at each stage are stored in a common network and used for process control. The number of tests at each stage to meet the production target depends on the actual test time and process time.

ZERA3:4_2007

Figure 3 - Highly advanced test system
supplied in Enel project

MOBILE TROLLEY TYPE
Meters are mounted on the mobile trolley at the start and then the operator moves the whole trolley from one place to another. This kind of test system saves time at each testing stage. The test time and process time determine the number of test systems at each stage. These kinds of test systems are flexible, easily adaptable and economical.

ADVANCED AUTOMATED TEST SYSTEM
The meter under test moves either on a conveyor belt or on a robotic platform in this type of test system. Each stage process time is very much controlled and optimised. These are effective where labour costs are high and there is a scarcity of skilled manpower.

CONCLUSION
The early involvement of a meter test solution provider will help in the design of an optimum solution that is cost effective and will avoid the unwanted compromises that may have to be considered to meet the production target. Decisions on the level of automation should also take into account the ever increasing direct/indirect costs to motivate and retain the skilled manpower of the company in comparison with the depreciation of test equipment.