3B. Frequency Operating Standards
Explanatory Note Clause 3B.1.1 requires AEMO to ensure the SWIS is operated at the Normal Operating Frequency Band of 50Hz and to achieve the Frequency Operating Standards. The obligation reflects good practice to operate as close as possible to 50Hz under normal operating circumstances to ensure that the levels of Essential System Services are sufficient (and to not continuously over-speed or under-speed mechanical equipment). |
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3B.1. Frequency Operating Standard responsibility
3B.1.1. Notwithstanding section 3B.3, AEMO must use reasonable
endeavours to:
\(a\) ensure the SWIS is operated with a SWIS Frequency of 50 Hz except under Controlled Circumstances; and
\(b\) achieve the Frequency Operating Standards set out in this Chapter
3B.
3B.1.2. The Frequency Operating Standards set out in this Chapter 3B
only apply to Embedded Systems and Disconnected Microgrids when they are connected to the SWIS.
Explanatory Note The Frequency Operating Standards in section 3B.2 relate to existing settings in the SWIS with the exception of the Normal Operating Frequency Excursion Band, for which there is currently no equivalent. This term provides an absolute target or reporting level for normal operations when the system is not operating within the Normal Operating Frequency Band, which is 99% of the time. This allows for the specification of performance targets around the remaining 1%. The Frequency Operating Standards are set out in Table 1 and Table 2, Appendix 13. |
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3B.2. Frequency Bands
3B.2.1. The Normal Operating Frequency Band is the normal frequency
operating range set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.2.2. The Normal Operating Frequency Excursion Band is an allowable
frequency operating range where no action or response is required by AEMO for infrequent or momentary excursions outside of the Normal Operating Frequency Band. The frequency operating range and duration are set out in Table 1, Appendix 13 for the SWIS.
3B.2.3. The Credible Contingency Event Frequency Band is the allowable
frequency operating range where there has been a Credible Contingency Event on the SWIS. The frequency operating range and duration are set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.2.4. The Island Separation Frequency Band is the allowable frequency
operating range immediately following a Separation Event on the SWIS which creates one or more Islands. The frequency operating range and duration are set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.2.5. The Extreme Frequency Tolerance Band represents the frequency
operating range that applies to the SWIS Frequency in respect of clause
3B.3.9. The frequency operating range and target timeframes to Stabilise
and Recover are set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
Explanatory Note Section 3B.3 sets out the bounds of the frequency bands and performance parameters for each frequency band. The section refers to the Frequency Operating Standards in Table 1 and Table 2, Appendix 13. The current SWIS settings are adopted for each band except for the Normal Operating Frequency Excursion Band which is a new band as noted above. |
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3B.3. Required SWIS Frequency outcomes
3B.3.1. Other than for an Island, while in an Emergency Operating State
or during a system restart, the Accumulated Time Error must be less than 10 seconds for 99% of the time over any rolling 30-day period in the SWIS.
3B.3.2. Subject to clause 3B.3.3, the SWIS Frequency must not exceed the
Normal Operating Frequency Band in accordance with the relevant requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.3.3. The SWIS Frequency may exceed the relevant Normal Operating
Frequency Band following the occurrence of a Contingency Event.
3B.3.4. Subject to clause 3B.3.8, the SWIS Frequency must not exceed the
Normal Operating Frequency Excursion Band, and must Stabilise, in accordance with the relevant requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.3.5. Subject to clause 3B.3.6, for any Credible Contingency Event,
the SWIS Frequency must not exceed the relevant rate of change requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.3.6. Clause 3B.3.5 does not apply to the initial formation of an
Island following a Separation Event.
3B.3.7. Subject to clause 3B.3.8, the SWIS Frequency must not exceed the
Credible Contingency Event Frequency Band, and must Stabilise and Recover, in accordance with the relevant requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.3.8. For the avoidance of doubt, the requirements in clause 3B.3.4
and clause 3B.3.7 do not apply where a Multiple Contingency Event occurs.
3B.3.9. Following a Separation Event, an Island is permitted to be
temporarily de-energised with frequency subsequently required to be restored to the relevant requirements set out in Table 2, Appendix 13 for an Island as soon as practicable.
3B.3.10. Subject to clause 3B.3.9, if there is a Separation Event, SWIS
Frequency must not exceed the Island Separation Frequency Band, and must Stabilise and Recover, in accordance with the relevant requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island.
3B.3.11. For a Non-Credible Contingency Event or Multiple Contingency
Event, reasonable endeavours must be taken to maintain the SWIS Frequency in accordance with the Extreme Frequency Tolerance Band, and to Stabilise and Recover the SWIS Frequency in accordance with the relevant requirements set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island. For the avoidance of doubt, the use of load shedding is acceptable in order to meet the requirements of this clause 3B.3.11.
3B.3.12. Based on the readings recorded in AEMO’s SCADA system, a
Contingency Event, including a Credible Contingency Event, Separation Event, commences at the time SWIS Frequency exceeds the frequencies in the Normal Operating Frequency Excursion Band set out in Table 1, Appendix 13 for the SWIS and Table 2, Appendix 13 for an Island, and ends at the time at which SWIS Frequency Recovers.
3B.3.13. For the avoidance of doubt, reasonable endeavours in this
section 3B.3 includes allowance for avoiding pre-contingent load shedding, or to prioritise restoration of load, over meeting the Frequency Operating Standards in an Island.