Page 23 of 190 Report No.: 6068396.50 TRF No. G99/1-4_V1.0 G99/1 Clause Requirement - Test Result - Remark Verdict 9.5.7 Various measures may be used, where reasonably practicable, to prevent or mitigate system instability. These may include Distribution Network and Power Generating Module solutions, such as: (a) from the Distribution Network at the Connection Point.
improved fault clearance times by means of faster protection; (b) improved performance of Power Generating Module control systems (excitation and governor/prime mover control systems; Power System Stabilisers to improve damping); (c) improved system voltage support (provision from either Power Generating Module or Distribution Network plant); (d) reduced plant reactance’s (if possible); (e) installation of protection to identify pole-slipping; (f) increased fault level infeed.
In determining mitigation measures which are reasonably practicable, due consideration should be given to the cost of implementing the measures and the benefits to the Distribution Network and Generators in terms of reduced risk of system instability. P 9.6 Island Mode P 9.6.1 A fault or planned outage, which results in the disconnection of a Power Generating Module, together with an associated section of Distribution Network, from the remainder of the Total System, creates the potential for island mode operation.
It will be necessary for the DNO to decide, dependent on local network conditions, if it is desirable for the Generators to continue to generate onto the islanded DNO’s Distribution Network. The key potential advantage of operating in Island Mode is to maintain continuity of supply to the portion of the Distribution Network containing the Power Generating Module. The principles discussed in this section generally also apply where Power Generating Modules on a Generator’s site is designed to maintain supplies to that site in the event of a failure of the DNO supply.
P 9.6.2 When considering whether Power Generating Modules can be permitted to operate in island mode, detailed studies need to be undertaken to ensure that the islanded system will remain stable and comply with all statutory obligations and relevant planning standards when separated from the remainder of the Total System. Before operation in island mode can be allowed, a contractual agreement between the DNO and Generator must be in place and the legal liabilities associated with such operation must be carefully considered by the DNO and the Generator. Consideration should be given to the following areas: P