USER MANUAL - Fundamentals Ltd
Contents
1. Directly mounted on 60 1 split core CT Supplied with solid core internal CT and fixing kit c Nortech Management Limited document reference D_066_0067 issue 2 02. FIND nortech Electronic Earth Fault Indicator USER MANUAL Nortech Management Ltd Tadcaster House Keytec 7 Business Park Kempton Road Pershore WR10 2TA United Kingdom tel 44 0 8700 111 992 fax 44 0 8700 111 993 e mail info nortechonline co uk web site http www nortechonline co uk E amp OE December 1999 Nortech Management Ltd D_066_0067 issue 2 0 FIND USER MANUAL PAGE 1 Contents section page 1 PRODUCT BACKGROUND 2 2 OPERATION 3 overview principle of operation characteristics physical description operating curve micro processor 3 SPECIFICATION 6 earth fault sensitivity indication remote indication test feature reset features power supply installation construction sundries 4 TESTING 8 EMC approval short circuit tests 5 INSTALLATION 9 Positioning CT on cable FIND wiring connections FIND with internal solid core CT Split Core CT installation 6 ORDERING INFORMATION 13 c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 2 1 PRODUCT BACKGROUND When protection equipment trip circuit breakers during fault conditions reliable information regarding the fault location can reduce the time off supply experienced by electricity consumers The use of FIND indicators on underground cable distribution networks enables electricity utility engineers to quickly and accurately determine which section of the underground system is responsible for th
3. Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 12 5 4 Installation of Split Core Current Transformer 1 Sz Place jubilee clip around cable 2 Remove nut bolt and washers from lower circlip and take out bottom half of split core 3 4 Remove L brackets from top half of split core rotate 180 degrees and replace loosely so that the ears Check that the faces of the exposed core are clean and free of dust or dirt protrude from the split core Place top half assembly around the cable sliding the L bracket between the cable and jubilee clip Adjust L brackets until assembly feels firm on cable and tighten bolts accordingly 7 Offer up bottom half of split core squarely to ensure core face alignment making sure that the protective weatherproof gasket is not caught between them Once both halves are aligned fit nut bolt and washers to outer circlip and tighten gently until resistance is felt and core faces are firmly met Do NOT over tighten c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 13 6 ORDERING INFORMATION When ordering please specify the features required the following options are available 3 hour timed reset 24 hour timed reset DC voltage reset 12 48V dc for 500ms AC voltage reset 50 240V ac for 10 seconds 20mm glanded cable entry pre drilled Directly mounted on 60 1 solid core CT
4. ctual flash duration is 200ms The typical flash rates for any given indication period are as listed below It is possible to specify any flash rate duration combination please specify at time of ordering Indication Period Flash Rate 1 3 seconds standard 3 3 Remote Indication The alarm system automation contacts changeover are electrically separate from the internal circuitry and remain in the operated position for the duration of the indication period or until the unit is reset manually or electrically 3 4 Test Feature A battery test feature is provided by applying a small magnet over the word FIND on the front of the unit This causes the LED to flash The alarm system automation relay contacts are not activated during this test If the battery is healthy the LED will flash if battery volts are low the LED will remain on In the event of a fault and low battery volts the LED will remain on for the duration of the indication period 3 5 Reset Features 1 Self reset after the specified indication period 2 Manual reset by applying a magnet for more than 5 seconds 3 Automatic electrical reset optional on the application of a DC supply of 12 24 48V for 0 5 seconds or an AC supply of 50 110 240V for more than 10 seconds The type of electrical reset must be specified at time of ordering 3 6 Power Supply Lithium Thionyl Chloride battery or equivalent providing sufficient energy for at least 150 three hour operations
5. during the estimated 10 year life of the battery The battery is set in a silicon compound which may be cut away for battery replacement if necessary 3 7 Installation The FIND is attached via a CT to RMU s on the incoming or out going 11kV feeder The indicator can be supplied mounted direct on the front of the CT or separate with a termination box on the CT for applications where remote mounting of the indicator is required More details on the installation of the FIND and solid and split CTs are given later in the document 3 8 Construction The case is made of a strong durable plastic approximately 80mm x 80mm x 55mm deep the cover having 4 stainless steel screws which are outside the perimeter of the oil and water tight neoprene gasket seal The indicating LED is semi recessed for mechanical protection and offers a 180 degree viewing angle c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 7 3 9 Sundries The FIND is supplied with flying leads for the CT connections and a terminal strip for the remote contacts and voltage reset as standard although any combination of the two can be provided on request Pre drilled fixing holes can be provided to suit particular requirements c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 8 4 TESTING 4 1 EMC Approval The FIND has been tested and is compliant with IEC255 22 3 Class3 A copy of th
6. e Approval Certificate is attached at the end of this document 4 2 Short Circuit Tests The FIND has been tested in the short circuit testing laboratory at a major UK switchgear manufacturer The unit was connected via a 60 1 ratio 5VA solid core ring CT to an 11kV cable The indicator and CT combination was subjected to several short circuit test shots up to 13 1kA Both indicator and CT withstood these shots without damage No change in normal operating current was detected after the tests c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 9 5 INSTALLATION 5 1 Positioning the CT on the cable Earth fault current is returned to source through the path of least resistance When the fault occurs in a cable system the majority of return current will flow through the cable sheath thus resulting in a null output from a core balance CT as shown below Fault Current Return Fault Current MINIMAL OUTPUT This effect can be prevented if the cable earthing connection between the cable and adjacent switch is routed through the core balance CT as shown below Fault Fault Current Current Return Fault Current Return Fault Current Correct output Correct output c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 10 5 2 FIND wiring connections The FIND may be connected to a suitably approved 60 1 CT for use
7. e interruption to consumer supplies The faulty section can then be isolated and supplies to healthy sections of network restored Fault past these points c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 3 2 OPERATION 2 1 OVERVIEW The FIND has been developed to detect at a point on the 11kV underground network the passage of earth fault current The unit is self powered and operates by the application of a small voltage derived from a current transformer at the time of a through fault An indication of through fault is given by a flashing hyper bright LED for a pre set time period On completion of the time period the unit will self reset and is then ready to detect subsequent through faults The FIND may also be manually reset or automatically reset on the restoration of supply 2 2 PRINCIPLE OF OPERATION The device is triggered by the current produced from the secondary winding of a 60 1 ratio core balance CT mounted around the power cable The minimum trigger level has been set to be above the likely maximum level of zero sequence capacitive current under severe out of zone earth fault conditions Care has been taken to ensure that stray magnetic fluxes do not cause inadvertent operation or premature resetting of the device An internal lithium battery then powers a processor which is arranged to reset the device after a preset time delay typically 3 hours dependi
8. ment Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 4 2 5 FIND OPERATING CURVE Operating Time in Milliseconds 0 100 200 300 400 500 600 700 800 900 1000 Primary Amps c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL 2 6 MICRO PROCESSOR CONTROL PAGE 5 A new feature introduced in 1996 to the FIND range is micro processor control The micro processor E PROM replaces the timer counter used in FINDs up to this date All FINDs supplied from June 1997 will incorporate the micro processor feature The micro processor controlled FIND has the following benefits compared to the standard FIND The microprocessor allows the FIND to be tailored to exact customer needs without the delay of hardware modifications testing and recalibration Varying reset characteristics the mains AC reset time is normally 10 seconds providing immunity from unsuccessful reclosures The DC telecontrol reset is normally 0 5 seconds to allow for the usual 1 second pulse from telecontrol systems Self reset can now be programmed to such short periods thus providing a short alarm pulse for telecontrol systems Improved battery test reset facility When the test magnet is applied the micro processor is programmed to give a fast flashing rate during the battery test period After a few seconds it changes to a steady continuous indication drawing maximum current from the battery thus proving
9. ng on the requirement During the delay period the LED flashes to indicate the passage of fault current FINDs between the source CB and the fault will flash FINDs beyond the fault will not operate On completion of the timing period the unit self resets and is ready to detect any subsequent through faults The device may be prematurely reset manually by applying a small magnet over the word FIND on the front of the unit for approximately 5 seconds Where specified the optional electrical reset operates approximately 0 5 seconds after the 12 24 48V DC Telecontrol signal is applied or approximately after 10 seconds after the 50 110 240V AC mains supply is restored 2 3 OPERATING CHARACTERISTICS A Block Diagram is shown on the page 4 the operating curve is shown on the next page 2 4 PHYSICAL DESCRIPTION The indicator is supplied in a robust case the internal circuitry being solid state and epoxy resin encapsulated for environmental protection Leads and or terminals are provided for connection to the current transformer a remote alarm or system automation scheme and a reset signal when an electrical reset feature is specified Local indication is provided by means of a hyper bright light emitting diode LED The units back plate is used to mount the device in the chosen position either on the switchgear the substation wall or directly on a core balance CT Installation onto an existing CT is simple and inexpensive c Nortech Manage
10. the battery is healthy or otherwise If the FIND has operated and is already flashing then the faster flashing rate when the magnet is applied shows the unit is functioning correctly and when indication changes to a steady flash it shows that the unit has reset correctly Examples where the micro processor has been exploited to give enhanced performance for specific customer needs include the following Extended LED indication periods of up to 24 hours allowing field staff longer to reach sites during storm conditions In order to preserve battery life the flash rate decreases after 6 hours from once every 1 5 seconds to once every 10 seconds Very short reset times where the FIND is used exclusively with automation sequences Programming of the output contacts to reset for different criteria from the LED DETECTOR ama jue m gt P processon gt NDICATOR O CONNECTIONS a l TO CURRENT ae TRANSFORMER gt coe c NO NC ALARM CONTACTS c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 6 3 SPECIFICATION 3 1 Earth Fault Sensitivity Set to operate between 30 and 60 Amps primary current with a 60 1 core balanced CT at 1 5VA The device has a short initial time delay of approximately 50 ms 3 2 Indication As standard the Hyper bright LED flashes at a rate depending on the indication period specified The a
11. with EEFls Check with the CT manufacturer for suitability of purpose prior to installation If in doubt contact Nortech for advice The diagram below shows the wiring connections FIND TERMINAL ARRANGEMENT BATTERY CONNECTIONS LEFT TO RIGHT VIEWED FROM REAR BELOW BATTERY left ALARM NORMALLY OPEN ALARM NORMALLY CLOSED ALARM COMMON CURRENT TRANSFORMER CURRENT TRANSFORMER OPTIONAL NEGATIVE FOR DC RESET right OPTIONAL POSITIVE FOR DC RESET c Nortech Management Limited document reference D_066_0067 issue 2 0 FIND USER MANUAL PAGE 11 5 3 FIND supplied with solid core CT The FIND is delivered already assembled Screw the spigot projecting above the FIND into one of the earthing studs on the base of the cable box such that the FIND projects below the box and faces the required direction The FIND may be left or right mounted according to site conditions Connect the leads from the FIND to the CT Ensure the earthwire is connected to another earthing stud Use the clips provided to secure spare leads Connections are as follows left to right viewed from the rear of the FIND below the battery Alarm Normally open Alarm Normally closed Alarm Common Current Transformer Current Transformer Reset Reset I l I Earthing stud I I I I I I Earthwire 1 Leads from FIND gt er Base of Cable Box FIND unit c
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