Transcript Practical Testing Issues

Practical Testing Issues
Real Life Issues
Bob Beavers
June 12, 2016
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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
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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.
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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
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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.
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NCX-21 – 1500 AH – 5 hour rate to 1.81 vpc - 254 A
Temperature – ~73.5°F – (23°C)
Correction factor per IEEE 450 Kt=0.977
Corrected rate = 248.2A
790A design
772A tested
Amperes
650A Design
635A Tested
248.2A
Time
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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.
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