Nortech F10 User manual

© Nortech Management Ltd, United Kingdom
May 2013
www.nortechonline.co.uk
Doc ref: D_000800
F10
Earth Fault Indicator
USER MANUAL
Version 1.2

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 2 of 16
Publication Notice
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including, but not limited to, the implied warranties of merchantability and fitness for a particular
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described in this document at any time and without notice. These changes may be incorporated in
new releases of this document.
This publication could contain technical inaccuracies or typographical errors. NML shall not be
liable for any damages (including, but not limited to, consequential, indirect or incidental, special
damages or loss of profits or data) even if NML have been informed of their potential occurrence,
arising out of or in connection with this document or its use.
English Edition
IBM PC is a trademark of International Business Machines Inc.
Windows is a trademark of Microsoft Corporation.
All other trademark names used in this manual are hereby acknowledged.

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 3 of 16
Contents
1Description.......................................................................................4
2Operation.........................................................................................5
2.1 Local Indication ...........................................................................5
2.2 Indication Period .........................................................................5
2.3Reset .........................................................................................5
2.4 Current Transformers ...................................................................5
2.5 Sensitivity ..................................................................................5
2.6 Test ...........................................................................................6
3Operation worked examples ...............................................................7
3.1 Indication with no electrical reset ..................................................7
3.2 Indication with AC reset signal ......................................................7
3.3 Indication with DC reset signal ......................................................8
4Installation.......................................................................................9
4.1 Physical......................................................................................9
4.2 CT earthing.................................................................................9
4.3 CT connections .......................................................................... 10
4.4 Wiring connections .................................................................... 11
4.5 Enclosure Mounting.................................................................... 12
5Maintenance ................................................................................... 13
5.1 Technical Assistance .................................................................. 13
5.2 Simple Test............................................................................... 13
5.3 Primary Injection ....................................................................... 13
5.4 Replace battery ......................................................................... 13
5.5 Recycling.................................................................................. 13
6Specification................................................................................... 14
6.1 General .................................................................................... 14
6.2 EMC ......................................................................................... 14
6.3 Environmental........................................................................... 15
7Notices .......................................................................................... 16

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 4 of 16
1Description
The F10 battery powered Earth Fault Indicator enables electricity distribution
network engineers to quickly determine which section of the underground MV
network is responsible for the interruption of consumer supplies.
An indication of the passage of fault current is given by a flashing LED for a
pre-set time period. At the same time the relay contacts operate giving an
electrical remote alarm.
On completion of the time period the unit will automatically self reset and is
then ready to detect subsequent faults. The F10 may also be manually reset,
remotely reset via a telecontrol DC reset signal or on restoration of AC
supplies.
The F10 indicator is available for use with either a core balance CT or three
phase CTs.
A lithium battery provides power to the unit. The battery will provide up to 20
years life between changes.

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 5 of 16
2Operation
2.1 Local Indication
On detection of fault current above the earth fault sensitivity threshold and for
the minimum required duration the F10 will operate as follows: -
1Flashing LED with an interval of 1.5 seconds for the duration of the
indicating period.
2Volt free contacts operate during the indicating period.
2.2 Indication Period
The default value is 3 hours flashing when a fault is detected.
Different indication periods may be selected to suit local requirements either
at time of order or in the field using a laptop and the F10 Field Support Kit.
2.3 Reset
Automatic
The indicator returns to the ready state (LED not flashing, volt-free contacts
reset, ready to detect fault current) after the indication period has elapsed.
Manual
The F10 may be reset early, at any time during the indication period, by
pressing the RESET button on the front of the F10. Once the button is
released the F10 will be reset to the ready state.
Electrical
The F10 may be reset early, at any time during the indication period, by either
a DC pulse (from a telecontrol RTU) or on restoration of a local AC supply.
2.4 Current Transformers
The CT combination to be used is a factory option –check with Nortech for
suitable part numbers. The F10 is designed for use with either:
Core Balanced CT
One 60/1 core balance CT having a minimum rating of 1.5VA and an accuracy
of 10% up to 4 times primary current (10P4).
Switchgear Phase CTs
Three single phase CT (typically 500:1) supplied with the Ring Main Unit.
These CT arrangements should be tested by Nortech to confirm suitability
prior to use.
2.5 Sensitivity
The F10 is designed to operate at 45 Amps primary current. Exact operating
sensitivity can be affected by the model of CT used and fault characteristic.
The F10 requires the fault to be present for a minimum of 50ms, the operating
curve can be assumed to be close to definite time.

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 6 of 16
2.6 Test
A simple manual test of the F10 is achieved by pressing the TEST button.
When pressed the LED will flash, however the output contacts will not operate.
This simple test proves the processor, LED, test button and battery are
healthy. It does not test the integrity of the CT connections or output
contacts.
A primary injection into the CT arrangement is the best local test available.
Nortech supply a portable battery powered test set for this purpose.

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 7 of 16
3Operation worked examples
The examples below illustrate how applying electrical reset can affect
detection and indication of faults.
The examples assume the F10 is configured with a 3 hour indication period.
The three faults occur at 2 hour intervals. After Fault 1 supplies are lost for 1
hour. After Fault 2 supplies are lost for 5 hours except for a few milliseconds
while Fault 3 is on the network.
3.1 Indication with no electrical reset
time
fault current
time
LED indication
and relay contacts
3 hours 3 hours
Fault 1 Fault 2 Fault 3
Unit starts
indication for
fault 1
Fault 2 not detected as
already indicating
Reset at end of 3 hour
timer
Indications with timer reset only
3.2 Indication with AC reset signal
time
fault current
time
LED indication
and relay contacts
time
AC supply status
1 hour 3 hours
1 hour
Fault 1 Fault 2 Fault 3
AC supply restored
Reset occurs 10 seconds
after AC is restored
No Reset as AC is on for
<10 seconds
AC supply lost when fault
occurs
AC supply restored
AC on for less than 10
seconds
Indications with AC reset connected

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 8 of 16
3.3 Indication with DC reset signal
time
fault current
time
LED indication
and relay contacts
time
DC reset signal
Fault 1 Fault 2 Fault 3
In all cases RTU sends DC
reset signal as soon as F10
indication is detected. F10
resets within 1 second of
DC reset signal
Indications with DC reset connected

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 9 of 16
4Installation
4.1 Physical
The F10 has an outer polycarbonate enclosure. The electronics are
encapsulated in the lid. The LED and buttons are located on the front of the
F10.
The F10 should be mounted for good visibility and as close as practical to the
CT.
4.2 CT earthing
For safety reasons, it is normal practice for the CT to be mounted in a
position over the cable sheath or screening tape, and in accordance
with local safety regulations.
When an earth fault occurs in a cable network the majority of return current
will flow through the cable sheath, thus resulting in a null output from the
core balance CT, as shown in the figure below.
INCORRECT Earthing
Incorrect Earthing
This effect can be prevented if the cable earthing connection between the
cable and adjacent switch is routed through the core balance CT shown below.
Correct Earthing
Correct Earthing
Where single core cables are used, each sheath earth-wire must be routed
through the single core balance CT.

F10
Earth Fault Indicator
© Nortech Management Ltd, United Kingdom
Page 10 of 16
4.3 CT connections
The CT arrangement the F10 will be used with is a factory set option.
Wire the summated output from the
CT secondary’s to the CT terminals
of the F10.
The current transformers should be
connected as shown in the diagram,
it is important that the polarities are
as shown.
Wire the output from the CT secondary
to the CT terminals of the F10.
3 phase CT connections
Single core balanced CT connection