Final Draft Report ASSESSMENT SUMMARY Hydro One Networks ...

Burlington TS Overload Protection/Load Rejection scheme(CAA ID Number: 2006-EX298)Hydro One indicated that this proposed scheme is intended as a back-up or insurance policy in the case of an abnormal oremergency situation where pre-contingency control actions (e.g. load transfer and/or opening A1A2 or H1H2) areunavailable to minimize post-contingency loads below the 15-MIN LTR of the autotransformers.4.0 ASSESSMENTAs per NPCC criteria the proposed scheme is deemed a type 3 SPS. The failure of the proposed scheme will not affect theinterconnected power system since these autotransformers serve the Burlington local area. However, IESO's "OntarioResource and Transmission Assessment Criteria" document # IMO_REQ_0041 stipulates in section 3.4.1 that "A SPSproposed in a connection assessment must have full redundancy and separation of the communication channels, and mustsatisfy the requirements of the NPCC Type I SPS criteria to be considered by the IESO". The proposed scheme does notmeet these requirements.As shown in Table 3, the 15-MIN and 10-DAY LTRs of the four autotransformers at Burlington TS are limited to valuessignificantly lower than the 2 pu trigger values of the proposed scheme. It can also be observed that the 15-MIN LTRs arenot much higher than the continuous ratings.Burlington TSExisting ratings of autotransformers 2(limited by 115 kV elements)See note 2Continuous(MVA)10-Day LTR (MVA)15-Min LTR (MVA)T4 250 261 272T6 215 256 289T9 250 256 265T12 250 257 267Table 3: Existing Ratings of Autotransformers at Burlington TSThe proposed scheme could result in an autotransformer loaded above its 15-MIN LTR. For certain load conditions, theoperation of the proposed scheme may reduce the loading below the 2 pu point but not below the 15-MIN LTRs of theautotransformer.5.0 CONCLUSIONSThe proposed scheme does not meet the criteria for a type 1 SPS as stated in section 3.4.1 of the "Ontario Resource andTransmission Assessment Criteria".The operation of the proposed scheme could result in a load level on an auto-transformer that is above its 15-MIN LTR butbelow the 2 pu level. Therefore, post-contingency control actions such as load shedding or transfers may still be required.6.0 REQUIREMENTSHydro One Networks Inc. must notify the IESO as soon as it becomes aware of any changes to the assumptions made in theconnection assessment. The IESO will determine whether these changes require a re-assessment.2 The 10-DAY and 15-MIN LTRs for T6 after it is upgraded will be listed in CAA report # 2006-EX299. These ratings are subject tochange.