Power System Security Guidelines - Approved for distribution and use by:

Transmission Line Outages opening a Bus Tie connection When the outage of a transmission line results in the opening of a bus tie connection and the nature of the outage is such that the transmission line can be isolated and the circuit breakers forming the bus tie connection can be reclosed, then the TNSP should consider returning that bus tie connection to service in order to increase the resili. [...] Example (1) If the trip of a transmission element and a network element in the distribution system has no greater impact on security of the transmission network than the trip of the transmission element on its own, then AEMO will not consider the distribution element as part of the contingency event for the purpose of classifying the event as either a credible contingency event or non-credible con. [...] Example (2) AEMO | Doc Ref: SO_OP_3715 | 20 March 2024 Page 14 of 67 Power System Security Guidelines If the disconnection of load at the same time as the trip of a transmission element has no greater impact on security of the transmission network than the trip of the transmission element on its own, then AEMO will not consider the disconnection of this load as part of the contingency event for th. [...] If the post-contingency power flow through a network element is above the continuous rating but within the short term rating, such outages will be permitted to proceed subject to TNSPs providing a suitable contingency plan detailing the method for bringing the power flow through the network element to the continuous rating within the required time frame. [...] Frequency Control AEMO dispatches FCAS in order to: • Control the minute to minute variations of power system frequency as a result of the continuous changes in load of the power system to within the Normal Frequency Band under steady load.