Page 22 of 190 Report No.: 6068396.50 TRF No. G99/1-4_V1.0 G99/1 Clause Requirement - Test Result - Remark Verdict 9.5.4.1 The range of initial operating conditions should be based on those which are reasonably likely to occur over a year of operation. Variables to consider include system loads, system voltages, system outages and configurations, and Power Generating Module operating conditions. P 9.5.4.2 The system disturbances for which stability should be maintained should be selected on the basis that they have a reasonably high probability of occurrence.
It is recommended that these include short-circuit faults on single Distribution Network circuits (such as transformers, overhead lines and cables) and busbars, that are quickly cleared by main protection.
P 9.5.5 With the system in its normal operating state, it is desirable that all Power Generation Modules remain connected and stable for any of the following credible fault outages, (a) any one single circuit overhead line, transformer feeder or cable circuit, independent of length, (b) any one transformer or reactor, (c) any single section of busbar at or nearest the point of connection where busbar protection with a total clearance time of less than 200ms is installed, (d) if demand is to be secured under a second circuit outage as required by EREC P2, fault outages (a) or (b), overlapping with any pre-existing first circuit outage, usually for maintenance purposes.
In this case the combination of circuit outages considered should be that causing the most onerous conditions for System Stability, taking account of the slowest combination of main protection, circuit breaker operating times and strength of the connections to the system remaining after the faulty circuit or circuits have been disconnected. P 9.5.6 It should be noted that it is impractical and uneconomical to design for stability in all circumstances. This may include double circuit fault outages and faults that are cleared by slow protection.
Power Generating Modules that become unstable following system disturbances shall be disconnected as soon as possible to reduce the risk of plant damage and disturbance to the system. P