Quantcast Section 6: Troubleshooting Procedures for Series Lighting Circuits

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General. This section contains general troubleshooting procedures for isolating a fault
in all types of airport series lighting circuits. The troubleshooting procedures contained in the
following paragraphs provide detailed step-by-step procedures for isolating a fault. The
procedures are based on the assumption that the only available information about the trouble is a
report specifying which circuit is not operating satisfactorily. The tests start with a check in the
vault. It is presumed that the problem is more involved than a burned-out lamp, although these
procedures will result in isolating a burned-out lamp if that is the problem. There are some
lighting systems that use shielded conductors, the following general procedures can be used for
both shielded and non-shielded systems. However, some shielded systems are unique, and local
maintenance procedures should be established.
Safety Warning. Troubleshooting tests in this chapter often involve voltages that are
dangerous. Safety precautions must be exercised for the protection of personnel and equipment.
Personnel performing the testing and troubleshooting procedures must be experienced in high-
voltage techniques or must be adequately supervised. Maintenance personnel should be
thoroughly trained in emergency procedures for treatment of electrical shock.
Initial Fault Isolation
Initial Fault Isolation Procedure
a) Select the circuit to be tested and set the brightness switch to 100 percent intensity.
b) Energize the regulator and measure the load current. Be sure the current is set to
the values defined in par. 5.6.1. If the load current is normal, proceed to step d. If the load
current is out of tolerance, adjust the current according to the procedure in the instruction
c) If the load current cannot be brought into tolerance, short-circuit the output of the
regulator for the circuit being tested. Energize the regulator and measure the short-circuit current
for each brightness setting.
(1) If the current is satisfactory for each brightness setting, then the regulator,
incoming primary voltage, input voltage circuit breakers and relays are functioning properly.
The protective and brightness controls from the control panel are also satisfactory, therefore, the
fault is probably in the series circuit.
(2) If the current is satisfactory for one or more brightness setting, but it is too
high, too low, or zero for other settings, and the input voltage and protective controls are
satisfactory, then the regulator brightness controls are probably at fault.
(3) If the current is appreciably higher or lower than specified for all brightness
settings, then the wrong input voltage is being used (where applicable), the input voltage has
changed, or the regulator is not operating properly.
(4) If the current reads momentarily and then becomes zero for all brightness
settings, then the remote-energizing controls, the protective relays, or the regulator are defective.
The airfield load circuit may also have an open in the series circuit.
(5) If the current is zero at all times for all brightness settings, then the fault is in
the incoming primary voltage, the energizing controls, the regulator, or the protective relays.
The airfield load circuit may also have an open in the series circuit.


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