Protection System Maintenance (PRC-005-2) – So many questions and so little time
With the FERC approval of PRC-005-2, with the stated purpose “To document and implement programs for the maintenance of all Protection Systems affecting the reliability of the Bulk Electric System (BES) so that these Protection Systems are kept in working order,” our industry faces several daunting questions:
- What is a Protection System Maintenance Program (PSMP)?
- What is a performance-based maintenance method and should I use it or stay with the time-based maintenance method?
- And when reading the following—”R1.2 Include the applicable monitored Component attributes applied to each Protection System Component Type consistent with the maintenance intervals specified in Tables 1-1 through 1-5, Table 2, and Table 3 where monitoring is used to extend the maintenance intervals beyond those specified for unmonitored Protection System Components”—What does it want us to document, and do we want to extend the maintenance intervals beyond those specified for unmonitored Protection System Components?
In 2007, we were required to define maintenance and testing intervals and their basis. Version 2 has now dropped that requirement and replaced it with easy to understand periods and associated actions. Like many of you, I was delighted to see longer unmonitored periods when compared to what is currently used. We all like options until a decision needs to be made. Monitored or unmonitored, performance-based or time-based; but which approach best fits the situation at hand? For some the answer is easy. Take, for example, an Independent Power Producer (IPP) that:
- Doesn’t use protection system communications
- Inspects their batteries every 1-2 months
- Tests the batteries every 2-3 years, and
- Tests the relay settings, sensing devices, trip coils, and circuits every 3-5 years
It makes sense for this IPP to declare in their PSMP that maintenance intervals not be extended beyond the unmonitored time frames. If the PSMP sticks with a time-based maintenance method, the number of times testers need to be engaged or contracted is less than what is required for the performance-based maintenance method. On the opposite side of the decision making process is a transmission entity with hundreds of substations that use communication links integral to their protection systems. Given the effort required to test all relays within the 6-year time period, the performance-based maintenance method may be the more attractive approach for scheduling reasons while maintaining BES reliability. Since the unmonitored communication period for verifying communication’s system functionality is 4 months, and given the high number of potential relay communication links, opting for extended periods for existing monitored communications might be a real cost saver since the 4-month requirement disappears and the 6-year performance period becomes 12 years if their status is monitored. A suggested approach for documenting the Protection System Maintenance Program (PSMP) is to divide it into four sections:
- Document which maintenance method is being used for component types when the option exists
- Document where monitoring is used to extend the maintenance intervals beyond those specified for unmonitored Protection System Components and how the monitoring, alarming and response is accomplished
- Document for each existing unmonitored component type the maximum maintenance period and maintenance activity and
- Document for each existing monitored component type the maximum maintenance period and maintenance activity