DTEC Ltd.
GFMIV
Ground Fault Monitoring
And Interruption System
CONTENTS
1.0 Ground Fault Monitor
and Interruption Manual............ 3
1.1
Introduction:.............................................................................................. 3
1.2
Specifications:.......................................................................................... 3
2.0
Installing GFMIV........................................................... 4
2.1
General Information................................................................................. 4
2.2
Rear Panel Connections:....................................................................... 4
2.2.1
Relay Common and Normally Closed Terminals:................ 4
2.2.2
Sense Circuit Terminals:........................................................... 4
2.2.3
Chassis Reference:.................................................................... 5
2.2.4
Power Cord Connection:........................................................... 5
2.3
General Operation and Front Panel Description:............................. 5
2.3.1
Power Switch and Light............................................................. 5
2.3.2
Reset Button:............................................................................... 5
2.3.3
Channel Indication Lights:........................................................ 6
2.3.4
Channel Select Rotary Switch:................................................ 6
2.3.5
Panel Meter:................................................................................. 6
2.4
Sense Blocks:........................................................................................... 6
3.0
Panel Drawings............................................................. 7
Fig.
1. Rear Panel Connections................................................................... 7
Fig.
2. Front Panel.......................................................................................... 7
Appendix
A Circuit Drawings............................................. 7
Fig.
3. Sense Block Wiring........................................................................... 8
Fig.
4. System Block Diagram..................................................................... 9
Fig.
5. Ground Fault Monitor Wiring Diagram......................................... 10
Drawing
Following Page:.............................................................................
Fig.
6. Ground Fault Relay Board Schematic......................................... 11
Fig.
7. Ground Fault Monitoring Board GA.............................................. 12
Fig.
8. Ground Fault Monitoring Board
Schamatic................................ 13
Fig.
9. Ground Fault Monitoring Termination
Board Schematic........ 14
Appendix
B GFMIV Setup Procedures............................... 15
Appendix
C Trouble-Shooting............................................ 18
Power
Failure................................................................................................... 18
Incorrect
LED Operation............................................................................... 18
Incorrect
Analog Meter Operation.............................................................. 19
Override
Condition......................................................................................... 19
Appendix
C Optional DC Relay Outputs............................. 20
1.0 Ground Fault Monitor and Interruption Manual
1.1 Introduction:
This document
contains setup, wiring diagrams and an
overview of the operation for the GFMIV Ground Fault Monitoring and
Interruption System. The ground fault
system is intended to protect equipment and people from failure or injury. The system measures and indicates the amount
of "leakage" résistance to the reference chassis ground. The system also provides the interruption of
a faulty circuit by means of interrupting a path to a contactor or switching
device.
1.2 Specifications:
Mechanical:
Dimensions: 19"
wide x 5.22" height x 18" deep.
Weight:
Electrical:
Power input: 120
Vac @ 60 Hz @ 1amps
Fuse: 250 Vac @ 3amps AGC
Number
of circuits: 8 individual sense
circuits/8 individual relay contacts
Monitored
circuits: 5 to 1000 Vdc and/or 24 to
3000 Vac 1 or 3 phase @ 60 Hz
(Higher
voltages available)
Interruption
point: Factory set 500 Kohms
Output
Relay: 240 Vac @ 10 amps Note:
(optional
switching to 480VAC @ 25Amps)
Optional
2.0 Installing GFMIV
2.1 General Information
Installation of
the ground fault monitoring system requires the connection of the power cord,
chassis reference, relay output circuits and sense inputs to the correct sense
blocks. These sense blocks are different
for Single phase/DC circuits and 3 phase circuits. The sense blocks are installed between the
monitored circuit and the sense inputs.
The typical connections for these blocks are in Appendix A. The relay outputs are triac switches that
open upon a ground fault condition.
Typical installation is to connect the coil of a contactor through this
relay and hence be interrupted and disconnected if a ground fault condition
arises.
2.2 Rear Panel Connections:
The
rear panel has connections for 8 - Relay Common Terminals, 8 - Relay Normally
Closed Terminals, 8 - Sense Circuit Terminals,
2 - Chassis Reference Terminals and a 120 Vac power cord. The block diagram and examples for the rear
panel wiring is located in Appendix A. There can also be connections fro the
Optional DC Relay contacts.
2.2.1 Relay Common and Normally Closed Terminals:
The ground fault
system can monitor up to 8 independent
AC and/or DC circuits. Each
circuit has a solid state relay with a triac output that can interrupt the
corresponding channel if a ground fault condition appears. Typically the Relay Common will connect to a
power source (line) that enables a contactor or switching device. The Normally Closed will connect to one side
of the coil or switching device. If no
ground fault condition is present the path will be completed by the solid state
relay closing. If a ground fault
condition is present the path will be interrupted by the solid state relay
opening. See wiring example in the
drawing appendix A. The solid state relays can only switch off AC circuits.
2.2.2 Sense Circuit Terminals:
The sense circuit
inputs should be connected directly to the sense blocks via a 22 to 20 gauge
wire. The sense blocks are then
connected to the monitored circuit. See
appendix A for connection to circuits.
Using Twisted pair wire shielded to chassis ground will reduce the
chances of an erroneous GFI trip.
2.2.3 Chassis Reference:
The chassis
reference input is essential for proper operation of the ground fault system
and must be connected to the system chassis ground or chassis ground to be
referenced. Typically this is the
chassis ground of the hull, umbilical, rack etc. The 2 terminals are tied together inside the
unit so connection of either terminal will be correct. If this terminal is not connected to chassis
ground the ground fault system will not function correctly.
This terminal is not internally tied to the chassis ground connection on
the power cord even though most likely these are the same. This is done to allow the user to choose the
least electrically noisy contact to use for the chassis ground connection.
2.2.4 Power Cord Connection:
The power plug
connection is a standard power supply cord set.
The input power of 120 Vac 60 Hz @ 1 amps must be stable and protected
if possible for proper use. The power
cord connector contains an integrated pull-out fuse holder with fuse and a
spare fuse. This fuse rated for 3 Amps
and is the only fused associated with the system.
2.3 General Operation and Front Panel Description:
The operation of
this ground fault system is to display and interrupt an electrical circuit if
there is a resistance of 500 Kohms between a conductor and chassis ground. The channel with the ground fault will
illuminate a Light on the front panel, and, with that channel selected by the
rotary switch the resistance will be indicated on the panel meter. The meter can only indicate one channel at a
time. Use the selector to choose the
channel to have displayed by the panel meter.
The front panel contains the power switch and light, reset
button, channel indication lights, rotary switch for analog channel select, and
analog panel meter.
2.3.1 Power Switch and Light
The power switch
and light indicate whether the unit has power to it. It is critical that the 120 Vac be stable and
constant as fluctuations in this level could cause the unit produce incorrect
readings. If the light does not
illuminate after throwing the switch check to ensure that the power cord is
plugged in and the fuse is not blown or incorrectly installed.
2.3.2 Reset Button:
The reset button
function is to reset the solid state relay board to the normally closed
position after it has been interrupted.
If the ground fault that caused the interrupt has been repaired or
corrected the reset button is depressed to resume proper operation. While the reset button is being depressed it
is possible to "override" the relay output and force it closed. Operators must be aware of this state as you
could override a interrupted circuit which still has a Ground Fault Condition.
2.3.3 Channel Indication Lights:
An illuminated
red light indicates that the ground fault level of that channel has reached 500
Kohms or below and the circuit has been interrupted. The channel will stay interrupted until the
reset button is depressed and the light goes off. If the light does not go off after the reset
button has been depressed then the channel still has a ground fault present and
should be checked more thoroughly.
2.3.4 Channel Select Rotary Switch:
The rotary switch
selects which analog value is displayed on the analog panel meter. The switch can be rotated to any of the 8
sensed circuits and the corresponding resistance value of that circuit will be
displayed on the panel meter.
2.3.5 Panel Meter:
The panel meter
displays the resistance value of the circuit selected.
2.4 Sense Blocks:
A sense block is
required for each channel to be monitored and sense blocks may vary from
circuit to circuit due to the type of circuit to be monitored. It is essential that the proper sense blocks
are used in each circuit or incorrect and faulty readings could result. The input resistance the sense circuit
requires for proper measurements is 600 Kohm, therefore; in a DC or 1 phase AC
circuit the 2 resistors must be 1M2. In a 3 phase AC circuit the 3 resistors
must be 1M8. For monitored circuits up
to 1000 volts use 1/2 watt resistors, for monitored circuits up to 2000 volts
use 1/2 watt resistors and for monitored circuits up to 3000 volts use 1 watt
resistors. Try to keep the sense blocks
close to the high voltage and use 22 to 16 gauge wire for the sense wire to the
GFM unit. This keeps the high voltage
within the designated area. For
connection examples see appendix A. The
resistors must be appropriately voltage sized.
3.0 Panel Drawings
Fig. 1. Rear Panel
Connections
