INSTRUMENT TRANSFORMER METERING IN METALCLAD SWITCHGEAR

In 1958 the Meter and Service Committees of EEI and AEIC issued Guide for Specifications for Revenue Metering Facilities Installed in Metalclad Switchgear. This guide states the principal objectives to be attained:

1. That a separate sealable compartment be provided exclusively for revenue metering equipment when mounted within the switchgear;

2. That space be provided within the compartment sufficiently large to accommodate separately the installation of any standard current transformers and any standard voltage transformers required for metering;

3. That space be provided within the compartment for the installation of separate, isolated voltage transformer fuses, where required;

4. That, where required, adequate space and panel facilities be provided within the compartment to permit the installation of all necessary meters, instruments, auxiliary devices, or test facilities, of any type, whether they be front connected, back connected, surface mounted, or flush type;

5. That the arrangements be such that the secondary wiring may be installed in a manner to facilitate checking of connections.

By following these specifications, control of all metering transformers and conductors rests with the utility company.

When extremely high-capacity current transformers are used, it is essential that spacing of bus bars be adequate to avoid interference between individual transformers.

There are many advantages to be gained by mounting instrument transformers in the customer’s switchgear. Protection, appearance, and, in many cases, economy, may be the result.