Oncor Would Pay $130,000 Under Settlement With Texas Staff Concerning Incorrect Line Rating Which Led To Price Spikes

Oncor Electric Delivery Company would pay $130,000 under a settlement with Staff of the Public Utility Commission of Texas to resolve alleged violations of PURA § 39.151(d) and 16 Tex. Admin. Code § 25.503(f)(8) (TAC), relating to the provision of information to ERCOT, arising from an incorrect line rating, which contributed in part to certain price spikes

16 TAC § 25.503(f)(8) requires market entities, including transmission and distribution utilities, to provide accurate and factual information to ERCOT.

According to the settlement, on April 27, 2015, a multi-step upgrade to Oncor's 6-mile Glenhaven to CRMWD8 tap (6510_A) 138 kV transmission line, increased the nominal line rating from 178 Mega Volt Amperes (MVA) to 326 MVA.

As part of the upgrade, Oncor provided ERCOT with a change request to modify the data in ERCOT's network system model and ERCOT implemented this model change. In its real-time telemetry data, however, Oncor continued to provide ERCOT with the lower MVA rating after Oncor and ERCOT implemented the model change, the settlement states

ERCOT Protocols § 3.10.8.1(2) requires that ERCOT use the real-time telemetry data provided to it by Oncor, even if its network system model indicates something else.

On May 18, 2015 actual experienced load and wind deliverability varied from the ERCOT day ahead estimates in part due to weather conditions that included higher ambient West Texas temperatures. Load was higher than estimated from approximately 12:00 PM to 9:00 PM and wind generation output was lower than estimated from approximately 1:00 AM to 1:00 PM. The combination of these conditions contributed to the need for additional transmission capacity in West Texas.

Oncor's 6510_A line became the limiting element in a binding transmission constraint at approximately 10:00 AM on May 18, 2015.

ERCOT-wide real-time prices rose as high as $785 per MWh, with prices in excess of $200 per MWh for nineteen Security Constrained Economic Dispatch (SCED) intervals.

The independent market monitor concluded that the binding transmission constraint for the 6510_A line contributed to these prices in some of the intervals, the settlement states. Actual system conditions, including other transmission line outages and the load and wind variations from day ahead ERCOT estimates also contributed to these prices in some intervals.

In the normal course of reviewing and managing the constraint, ERCOT notified Oncor of a potential incorrect line rating at approximately 3:33 PM. Oncor corrected the real-time telemetered data approximately 58 minutes after notification by ERCOT, the settlement states

Prior to the ERCOT notification, Oncor asserts that it was unaware of the data discrepancy, the settlement states

In total, Oncor telemetered incorrect real-time data to ERCOT for twenty-two days, the settlement states

Since the May 18th event, Oncor has modified its process for real-time telemetry to help reduce the likelihood of future variations between network system model data and real-time telemetered data.

Oncor agreed to conduct audits on its line ratings every month for the six months following approval of the settlement agreement to help reduce reoccurrence of the issue. The audit will identify discrepancies between ERCOT's operating model and Oncor's operating model.

Docket 46189