Practical Testing Issues Real Life Issues Bob Beavers June 12,

Overview Failure to properly plan and prepare for a discharge test can result in: – Improper test conditions – Test interruptions Result – Retest – Extended out of service durations All of the items discussed here actually happened 2

Loss of 120 Vac Power Supply A high rate on a 250 volt battery required a master and a slave load bank. – Master and Slave Load banks connected to the same circuit breaker. – Circuit breaker tripped during the first minute. – All fans and all relays of master and slave units greater than circuit breaker rating Large load bank was connected to a power pack during an outage. – The 120 volt portion of the power pack tripped when a grinder was used and powered from the same power pack. 3

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Equipment issues Cable issues – Pin connectors not having continuity. Contactors were not energized when needed. Relay issues – Cracked relays that failed during the test Resistor issues – Open resistors that caused a delay in testing NOTE: Moving the large resistor banks results in shock to the equipment from – Elevators – curbs, – Thresholds – Sidewalks – Uneven roadway 7

Test current values Modified performance test – Adjusted peak current when temp was below 77F for a modified performance test. Result – the battery had to be recharged and the test rerun. Extended the DC system outage window. 8

248.2A 790A design 772A tested 650A Design 635A Tested NCX-21 – 1500 AH – 5 hour rate to 1.81 vpc A Temperature – ~73.5°F – (23°C) Correction factor per IEEE 450 K t =0.977 Corrected rate = 248.2A Time Amperes 9

Recommendations Power Supply – Verify current requirements and potential conflicts Pre-test checks – AFTER the equipment is in place – Verify all functions of the control system – Inspect Relays as well as verifying pickup upon demand – Measure resistor values for each resistance step Understand the testing requirements – The modified performance test requirements need to be understood and the limits of when correction factors can be used. 10