regulators consist of a complete maintenance pro-
circuits.
gram that is built around records and visual inspec-
(b) Second i s an amplifying section with or
tions. The program includes appropriate analysis of
without time delay, which amplifies the voltage sig-
these records.
nal.
(1) Record keeping. Equipment and system log
(c) Third is a motor drive which responds to
sheets are important and necessary functions of
the signal by moving a tap changer or induction
record keeping. The log sheets must be specifically
regulator in a direction to correct the voltage.
developed to suit auxiliary use.
5-15
TM 5-685/NAVFAC MO-912
(2) Troubleshooting. Use recognized industrial
Table 5-2. Switchgear equipment
practices as the general guide for servicing. Refer to
troubleshooting-Continued
manufacturer’s literature for specific information
Note
on individual voltage regulators. Troubleshooting
Refer to manufacturer’s li terature for
specific information on
procedures include the following:
individual equipment.
(a) Check voltage for compliance with manu-
facturer’s specifications.
(b) Check fo r 1oose or insecure electrical con-
RELAYS FAILING TO TRIP BREAKERS
nections.
Contacts improperly adjusted Adjust contacts. verify proper wipe (c) Check for correct setting, refer to manufacturer’s literature. Open or short circuit in relay con- Check to verify that voltage is ap-
(d) Check for unregulated voltage. Refer to
nections
plied and that current is passing
manufacturer’s literature.
through relay in question
(e) Check the enclosure. Should be weather
Improper application of target and
Verify proper tripping action of
tight.
holding coil
target and holding coi IS
(f) Check motor for proper operation and
Faulty or improperly adjusted tim-
If timing device is of bellows or
loose connections. Clean and lubricate as required.
ing devices
oil-film type, clean and adjust. if of
Refer to manufacturer’s literature for details.
induction-disk type, check for me-
chanical interference. Refer to
(g) Voltage regulators and associated equip-
manufacturer’s literature
ment are normally mounted within switchgear
NOISES DUE TO VIBRATING PARTS
equipment and are interconnected with different
Loose bolts or nuts permitting ex-
Tighten to proper torque value
components. The proper operation and trouble-
cessive vibration
shooting of voltage regulator equipment can depend
Loose laminations in cores of
Tighten loose nuts or core clamps
on these different components. Perform the proce-
transformers, reactors, etc.
to proper torque value
dures in the following table:
CONNECTIONS OVERHEATING
Table 5-2. Switchgear equipment troubleshooting.
Increase of current due to overload
Increase the carrying capacity (in-
conditions
crease the number or size of con-
Note ductors) Remove excess current
from circuit
Refer to manufacturer’s literature for specific information on individual equipment.
Connecting bolts and nuts not tight Tighten ail bolts and nuts to proper torque value
Cause Remedy
FAILURE IN FUNCTION OF ALL INSTRUMENTS AND DEVICES
WATTHOUR METER INACCURATE
HAVING POTENTIAL WINDINGS
Meter may be dirty or damaged Install new meter, return faulty Loose nuts, binding screws or bro-Tighten all loose connections to
meter to repair depot for repair and
ken wire at terminals
proper torque value or repair bro-
calibration
ken wire circuits
Faulty wiring or connections Inspect and repair as necessary
Blown fuse in potential transformer Renew blown fuses
circuit
WATTHOUR METER FAILS TO REGISTER
Blown potential transformer fuse, Renew blown fuses Check wiring Open circuit in potential trans-Repair open circuit and check en-
broken wires or other fault in con- and repair as required
former primary or secondary cir-
tire circuit for continuity and good
nections
cuits
condition
Wedge or block accidently left at
Remove wedge or block Verify that
BREAKER FAILS TO TRIP
time of test or inspection
meter is in good operating condi-
Mechanism binding or sticking Lubricate breaker mechanism; refer tion
caused by lack of lubrication to manufacturer’s instructions
DAMAGED CONTROL, INSTRUMENT TRANSFER SWITCH,
Mechanism out of adjustment Adjust all mechanical devices,
OR TEST BLOCKS
(toggles, stops, buffers, opening
Burned or pitted contacts Dress or clean burned contacts or
springs, etc.) according to manu-
replace with new contacts if neces-
facturer’s instructions
sary
Failure of latching device Examine surface of latch, replace
RELAYS FAILING TO TRIP BREAKERS
latch if worn or corroded. Check
Improper setting Adjust setting to correspond with
latch wipe, adjust according to
circuit conditions. Refer to manu-
manufacturer’s instructions
facturer’s instructions
Damage trip coil Replace damaged coil
Dirty, corroded or tarnished con-
Clean contact with knife or tile Do
tacts
not use emery cloth or sand-paper
5-16
TM 5-685/NAVFAC MO-912
Table 5-2. Switchgear equipment
(4) Frequency. Frequency of alternating cur-
troubleshooting-Continued
rent is indicated on a frequency meter. The meter
scale is usually graduated in 50/60 Hertz.
Note
(5) Speed. Rotational speed of the prime mover
Refer to manufacturer’s literature for specific information on is indicated by a tachometer in revolutions per
individual equipment.
minute (rpm). Generating systems covered herein
usually use an impulse tachometer, including the
inductor and eddy current types. These tachometers
use a magnetic pick-up to sense speed.
(6) Temperature. Several temperature values
Faulty connections (loose or bro-
Repair faulty wiring, tighten all
(including coolant, lubricating oil and exhaust) are
ken wire) in trip circuit
binding screws to proper torque
usually required to assure safe prime mover opera-
value
tion. Each value is monitored by a sensing device
OIL CONTAMINATED
with a remote indicator or thermometer. The sens-
Carbonization from too many op-
Drain oil and filter, clean or re-
ing device can be thermocouple or a combination of
erations place. Add fresh oil. Clean inside
sensing bulb and capillary tube.
of tank and all internal parts of
(a) Thermocouple. A thermocouple consists of breaker; refer to manufacturer’s
a pair of electrical conductors, each of different
instructions
metal, which are joined at the end adjacent to the
Condensation due to atmospheric Same procedure as above
temperature to be measured. A thermal emf is pro-
conditions
duced at the junction of the conductors. The other
Overheating Eliminate cause of overheating
end of each conductor is connected to a voltmeter
which measures and indicates the thermal emf.
5-7. Instrumentation.
(b) Sensing bulb and capillary tube. T h e
sensing bulb and capillary tube contain a specific
Switchgear instrumentation, based on the complex-
amount of liquid or gas whose pressure varies with
ity of the complete system, may include all or any
temperature. The variation appears on the ther-
combination of indicating, recording, and metering
mometer and represents the temperature of coolant,
instruments. Potential and current transformers
oil or exhaust.
are used to isolate instrument circuits from the
(7) Pressure. Pressure in the prime mover is
power circuit. Usually, the secondary winding of
indicated by sensing devices and remote gauges.
potential transformers is rated at 120 volts. Current
Usually a bourdon tube is used. The variation ap-
transformer output is 5 amperes.
pears on the gauge and represents lubricating oil or
a. Types of instrumentation. Instrumentation in-
other pressure. Other pressure values may be
cludes indicating and recording types.
shown on the system instrument panel depending
b. Application. Information related to instrument
on the type of prime mover and the overall system
transformer application is covered in paragraphs
requirements. These pressure values include start-
5-3 b( 2) and 5-3 c(2).
ing air, turbo boost, scavenging air, exhaust mani-
(1) Voltage. Voltage values are indicated by a
fold and fuel gas. Gauges or meters are used for
voltmeter.
indication as required.
(2) Current. Current values are indicated by an
(8) Fuel level. Various methods are used for
ammeter.
fuel level measurement. Fuel in underground stor-
(3) Power. Power values are described as watts,
age tanks can be measured by immersing a cali-
vars and power factor (refer to para 4-7 e for addi-
brated dip stick in the tank. For day tanks, a glass
tional information).
sight-gauge or a float actuated gauge can be used to
(a) Watts. Watts or kilowatts (units of electric
measure the quantity of liquid fuel, Remote indica-
power) are indicated by a wattmeter.
tors using pneumatic, electric or hydraulic devices
(b) Vars. V ars or kilovars (units of reactive
are also used.
power) are obtained by multiplying effective value
(9) Running time. The amount of time an aux-
of current, effective value of voltage and the sine of
iliary generating system operates is a required part
the angular phase difference between current and
of system record keeping. Time is usually recorded
voltage.
on a digital measuring device or counter located on
(c) Power factor. Power factor, the ratio of
the system instrument panel. Usually the counter is
active power to apparent power, is displayed on a
used with electric or electronic circuitry. An electric
power factor meter. The meter scale is usually
system usually has an AC synchronous motor that
graduated in percentage power factor.
is geared to the counter. Accuracy of motor and
TM 5-685/NAVFAC MO-912
counter depends on the frequency of the generator
stalled to protect generator stator windings from
output voltage. An electronic system also records
internal shorts and overheating are sensitive to
operating time on a digital measuring device. This
faults in the generator and do not respond to faults
system measures time by counting the number of
outside the generator. These relays act rapidly to
--
cycles produced by the frequency of the generator
prevent damage to the generator and isolate the
output voltage. Counter indications are propor-
generator from the system. Relay action includes
tional to frequency vs time.
de-energizing the generator field winding. Protec-
tive relays are provided in systems when reverse
5-8. Relays.
power flow occurs. Those relays operate on a succes-
Relays are used with the automatic controls for aux-
sion of power reversals and current impulses to
iliary power generating systems. A relay responds to
detect loss of synchronism. Protective relays include
electrical or other operating parameters and causes
the following types:
an abrupt change in the control circuits when the
(a) Overcurrent. Overcurrent relays function measured values change. A relay consists of a sens-when current flow exceeds the normal or desired
ing element and a control element with contacts.
value. Induction disk relays with time delay and
a. Types of relays. Relays used in switchgear in-cup type relays (without time delay) are known as
clude general purpose and protective types.
electromechanical type relays. Solid state relays are
(1) General purpose. General purpose relays
normally used on more recently installed equip-
function as part of regulation and verification de-
ment.
vices throughout the system including the prime
(b) Overvoltage. Overvoltage relays function
mover.
when voltage exceeds the normal or desired value.
(a) Industrial. Portions of electrical systems
Induction disk relays with time delay and cup type
are energized or de-energized under normal or ab-
relays without time delay are used.
normal conditions by relays. Since the relays are
(c) Undervoltage. Undervoltage relays func-
usually used with subsystems or equipment circuit
tion when voltage is less than normal or desired
breakers, the overall operating plan must be electri-
value. Induction disk relays with time delay may be
cally coordinated. Coordination is usually accom-
used in a balanced position between minimum and
plished by designing the system circuitry to selec-
maximum voltages.
tively initiate the opening or closing of the relays.
(d) Reverse power. Reverse power relays
Relays constantly monitor the power system.
function whenever power flows in the reverse direc-
- -
(b) Overload. 0 verload relays are used to
tion from normal or desired. These relays detect loss
provide overload protection for the auxiliary motors.
of synchronism.
When an overload condition occurs in any of the
(e) Underfrequency. Underfrequency relays
three phases in which heaters are inserted, it will
function whenever the desired frequency becomes
cause the relay to trip.
less than normal value. This condition is usually
(c) Time delay. Relays employed for time de-
the result of reduced prime mover speed and may be
lay purpose are usually solid-state type. Some pneu-
caused by the prime mover governor or excess elec-
matic relays may still be in use. Pneumatic relays
trical load.
utilize a bellows type arrangement to provide the
(f) Differential. Differential relays function
time delay. They can be adjusted for time periods of
due to the difference between two quantities of the
less than a second to several minutes.
same kind such as, two currents or two voltages.
(d) Solid-state. Solid-state relays derive their
Differential relays, usually used to detect stator
time delay from a combination of several electronic
winding electrical failure, respond to current per-
components. They are also adjustable between frac-
centage differences. Current or voltage transform-
tions of a second to several minutes.
ers used in differential network should be in
(e) Voltage sensitive. Voltage sensitive relays
matched sets. Percentage differential relays are
are used to sense an increase or decrease in a spe-
also used to prevent relay operation for faults due to
cific voltage. They provide an output signal when
current transformer ratio error outside the pro-
the voltages pass the preset level.
tected zone. In this application, the overcurrent re-
(2) Protective relays. Protective relays detect,
lay operates instantly when there is a bus short
isolate, and/or indicate abnormal electrical condi-
circuit but will not operate if a current transformer
tions. The operation of circuit breakers or other
secondary opens. The contacts of the two relays are
protective devices is initiated by relays as required.
connected in series.
Some of the electrical hazards protected against are
(g) Current balance. A current balance relay
short circuit, overcurrent, over or under voltage,
circuit monitors two or more current circuits and
---
and phase or frequency irregularities. Relays in-
provides an output if the difference between any
5-18
TM 5-685/NAVFAC MO-912
two exceeds the setting of the relay. The relay
(j) Note that differential relays are usually
senses the difference between the current of one
very sensitive devices that use polarized sensing
generator and the current of another generator or
circuitry. Repeat the pickup test. Use the second
the average of all other generators. Relay output
test for comparison with previous and future test
may be used to trip bus tie contactors and split a
data. Refer to manufacturer’s instructions.
parallel system to remove an unbalance.
c. Record keeping. Equipment and system log (h) Ground fault protection. Ground fault
sheets are important and necessary functions of
protection is usually provided by a ground sensor
record keeping. The log sheets must be specifically
relay which measures the sum of currents in the
developed to suit auxiliary use.
lines to the load in a three-phase system. Another
d. Troubleshooting. Perform troubleshooting pro-
relay is sometimes added to the transformer
cedures when abnormal operation of the system or
neutral-to-ground connection for backup.
equipment is observed. Maintenance personnel
b. Testing of relays. Periodic testing of relays is
must then refer to records for interpretation and
considered preventive maintenance. The preventive
comparison of performance data, i.e., log sheets.
maintenance program is built around records and
Comparisons of operation should be made under
visual inspections and includes analysis of the
equal or closely similar conditions of load and ambi-
records.
ent temperature. The general scheme for trouble-
(1) The frequency of testing is dependent on
shooting is outlined in the following table.
the variables involved i.e., type of relay, environ-
mental conditions, history, and experience. The am-
Table 5-3. Relay troubleshooting.
bient operating temperature must be recorded.
Most relays have draw-out construction so that a
Note
relay can be separated from its enclosure. Discon-
Refer to manufacturer’s literature for specific information on nection for test or repair is usually not required.
individual equipment.
(2) Checks and tests to be performed are deter-
Cause Remedy
mined by the type of relay. The schedule for perfor-
mance of tests should comply with the requirements
MAGNET-OPERATED INSTANTANEOUS TYPE
of AR 420-43. Proceed as follows:
High Trip Action
Faulty coil Install coil with correct rating
(a) Inspect the relay cover before testing. Re-
move dust and other foreign matter to prevent it
Low Trip Action
from entering the relay. Record the inspection re-
Shorted turns on high trip Test coil and replace with new coil if found defective
sults.
(b) Check relay for “flag” indication. Also,
Mechanical binding; dirt, corrosion Clean parts
check cover glass for fogging. If fogging is excessive,
Assembled incorrectly See manufacturer’s instructions
investigate the cause.
MAGNET-OPERATED INVERSE-TIME TYPE
(c) Check all connections for proper tight-
Slow Action Trip
ness. If necessary, tighten to proper torque value.
Fluid too heavy, vent too small, or Change fluid and open vent (d) Check a rmature and connect gaps. Com-temperature too low slightly, regulate temperature
pare with previous measurements. Adjust gaps if
Worn parts Replace and adjust
necessary and refer to manufacturer’s instructions.
(e) Check contacts for burned or eroded con-
Fast Trip Action
Worn, broken parts
Replace and adjust
dition. Burnish if necessary and refer to manufac-
turer’s instructions.
Fluid too light, vent too large or
Change fluid to proper grade Close
(f) Verify proper contact operation. Open or
temperature too high
vent slightly or regulate tempera-
ture. Clean dashpots and refill with
close contacts to observe proper trip or reclose ac-
fresh fluid or proper grade
tion and refer to manufacturer’s instructions.
(g) Apply current or voltage to verify that
THERMAL TYPE
Fails to Trip Causing Motor Burnout
pickup is within manufacturer’s tolerances.
Wrong size heater Check rating with recommenda-
(h) Reduce the current until the relay drops
tions on instruction sheet
out or fully resets. Verify that there is no binding
Mechanical binding; dirt, corrosion Clean and adjust
during operation and refer to manufacturer’s in-
structions.
Relay damaged by short circuit Replace relay
(i) Verify that related devices such as capaci-
Motor and relay in different ambi-
install motor and control near each
tors are functioning properly and refer to manufac-
ent temperature other or make temperature uniform
turer’s instructions.
for both
5-19
TM 5-685/NAVFAC MO-912
Table 5-3. Relay troubleshooting-Continued
tery. In addition, batteries provide power for
switchgear control and power to trip some circuit
Note
breakers. Most applications for auxiliary power use
Refer to manufacturer’s literature for specific information on some fo