PRC-005-2 is the revised NERC Standard for Protection Systems Maintenance and Testing.

PRC-005-2 states minimum requirements for maintenance for:

Protective Relays

DC Supplies

DC Control Circuits 

Current and Voltage Sensing Devices

Associated Telecommunications Equipment

The standard also states the maximum allowed time intervals between "hands-on" maintenance activity.

It is looking more and more like FERC is going to demand additional equipment be added to the latest revision of the present standard.

As of this writing, PRC-005-1 has been interpreted to require maintenance on batteries, but not chargers. Maintenance is required on protective relays, but not restoration relays (auto-reclosing relays). PRC-005-1 has been interpreted to require maintenance on protective relays that receive electrical inputs from voltage and current sensing devices, (not sudden-pressure relays).

The rationale of the Standard Drafting Team that made these interpretations was simple. They were not allowed to re-define the existing PRC-005-1, nor were they to create new definitions. They were charged with the job of interpreting the existing standard, based on the existing NERC definitions.

NERC has a firm definition of what constitutes a Protection System, and PRC-005-1 was written to require maintenance on a Protection System.

The drafting team noted that the Protection System definition presently specifies batteries. It does not specify battery chargers. Hence the interpretation states that battery chargers are not included within the scope of PRC-005-1.

Please note that the Regional Reliability Organization for your area may choose to have more stringent requirements.

Also note that the interpreting team is also the drafting team for PRC-005-2. The revised standard PRC-005-2 will have requirements for maintenance on battery chargers and any power supply system that supplies DC to the Protection System.

There have been published statements that both FERC and NERC were dissatisfied with the interpretations concerning auto-reclosing relays and sudden-pressure relays. There is a movement pushing to have these devices included within the requirements of PRC-005-2.

The eventual state of PRC-005-2 is unknown at this time, but prudent utilities will be making plans that these other devices may end up in PRC-005-2.