BESS testing triggers overnight outages

A planned testing on the power station’s new Battery Energy Storage System (BESS) that took place after midnight on Monday morning left a number of residents perplexed by the ensuing power cuts despite there being a warning from The Gibraltar Electricity Authority [GEA] ahead of the event.

The GEA has been conducting controlled live tests to integrate a BESS into its network, including simulations of engine failures at low-load periods.
The BESS acts as a large uninterruptable power source capable of providing an hour of Gibraltar-wide electricity supply in the event of a power cut.

That would provide a sufficient buffer on most occasions to enable engineers to get the system back up and running without the consumer noticing any glitch in supply.

The BESS’ capacity is 14 megawatts for one hour, approximately the size of one of the power station’s engines.
During Monday’s testing, the system performed within acceptable frequency limits up to 6MW.

However, at 12:20am, a simulated failure at 4MW triggered falling frequency protection, causing the temporary loss of two feeders. However, service was quickly restored after adjustments.
Further tests at 4MW–7MW were successful, but when the load reached 8MW, the BESS did not respond properly, leading to a frequency drop and a system-wide outage. Power was promptly restored.
BESS contractors are currently investigating the incident and implementing corrective measures.

The BESS is a zero-emission alternative to existing temporary diesel generators that provide grid support and stability services.

In a social media post on Sunday ahead of the tests, the GEA had warned that “while every effort is made to minimise the possibility of a disruption to electricity supply, a temporary interruption remains possible during the tests.”

“These tests are being carried out overnight to minimise any impact on households, businesses and essential services.”

The power cuts resulted in alarms going off, electronics beeping as they powered back up and lights sporadically being turned on. While not confirmed as the cause, some traffic lights were also out on Monday morning and internet speeds were also down.

“The Gibraltar Electricity Authority has been working closely with Battery Energy Storage System (BESS) contractors to optimise and program the integration of the BESS into the GEA network,” the GEA said in a statement on Monday.

“As part of this process, a series of controlled live tests have been conducted, including simulations of engine failures at low load levels during late-night and early-morning hours."
“These tests are designed to ensure that system parameters remain within established standards under varying operating conditions. “

“During testing last night [Monday morning] previous results at levels up to 6MW had remained within acceptable frequency ranges."

“At approximately 12:20am, a simulated engine failure was initiated at a 4MW load."

“This resulted in a frequency drop that activated the system’s falling frequency protection, leading to the loss of two feeders. Service was quickly restored after system parameters were reviewed and adjustments were made to BESS controls and instrumentation.”

“Testing then resumed, progressing from 4MW to 6MW and subsequently to 7MW, with BESS performance remaining within acceptable limits.”

“Upon increasing the test to 8MW, the BESS did not respond as expected, resulting in a frequency decline below network thresholds and causing a system-wide outage.”

“Our teams were quickly dispatched to the affected areas and restored supply promptly.”

“BESS contractors are actively investigating the incident to determine the cause of the failure and to implement corrective measures to prevent a recurrence.”