TP-6953 7/19132 Section 7 Troubleshooting
7.9 Troubleshooting—Protective Relays
Protective Relay Intended Function Potential Causes Troubleshooting
Reverse Power
(on the Decision-
Makerr 3500
controller:
Generator Total
Real Power:
Low Warning)
To trip the paralleling
breaker if a generator is
not producing absorbing
real power. A generator
should always produce
power while running. If
the generator is not
producing power, the
protective relay will trip
the paralleling breaker,
removing the generator
from the paralleling bus,
as it is not contributing
to the power output.
Incorrect Real Load Sharing
configuration.
The engine should be able to provide power individually. If so, the Real Load Sharing configuration is
probably incorrect.
A paralleled unit in a fixed power
mode (Baseload), set to a value
higher than required for actual
load.
Check modes on other controllers. Baseload mode on one generator may result in reverse power on
the other generators. Check Baseload setting is less than actual load.
Incorrect wiring to the CTs on one
or more units on the paralleling
bus (not necessarily the unit that
tripped on reverse power).
Load bank each generator individually. Power should read positive and accurately. Make sure that the
generator controller reads a unity power factor into a resistive load bank. If a load bank is unavailable,
make sure that phase powers are all positive and that phase power factors make sense.
Incorrect current meter calibration
for one or more generators in the
system.
Check current meter calibration according to the manual
Loss of fuel (run out of fuel, a
failed suction line, or failed fuel
supply component such as
injectors, carburetor, throttle
control, etc.).
The failed generator should be easily detected as it will shut down for underspeed or underfrequency
after the breaker trips. There will be no fuel pressure.
Check the fuel reservoir, fuel supply lines, and fuel supply components on the engine.
Check for related diagnostic messages (DTCs) from the ECU.
Electrical failure in the engine
ECU.
The generator will shut down for underspeed or underfrequency after the breaker trips. Fuel pressure
will be normal.
Check for related diagnostic messages (DTCs) from the ECU.
Mechanical problem in the engine. The generator will shut down for underspeed or underfrequency after the breaker trips. The crankshaft
maybeverydifficulttoturn.
Check for related diagnostic messages (DTCs) from the ECU.
Incorrect protective relay setting. Ensure that protective relay settings are determined by a comprehensive coordination study using
recent and accurate system data.
No speed control through,
replacement ECU not configured
correctly to accept CAN speed
commands, engine derates active.
Check ECU calibration file.
Over Power
(on the Decision-
Makerr 3500
controller:
Generator Total
Real Power:
High Warning)
To protect the generator
from overload conditions
that may result in
damage to the
generator.
Incorrect Load Management setup. Verify critical load is less than a single generator capacity. Load Management should be able to
remove enough load to allow a single generator to support it.
Verify correct wiring between load shed outputs and sw itching components.
Verify distributed loads and ratings are consistent with Load Management configuration/settings.
Failure of another generator. Check Load Management settings to ensure that all loads are shed quickly enough in the event of a
generator failure.
Check Generator Management settings to ensure the desired minimum number of generators is
selected.
Load growth in application. Verify that Load Management can shed enough load for a single generator to support it.
Incorrect protective relay setting. Ensure that protective relay settings are determined by a comprehensive coordination study using
recent and accurate system data with consideration for Load Management configuration.
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