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The detailed set-up of the 4-20mA is described below
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Digital Volt-Free-Contact Interface
Where a fault repeater exists, up to 12 digital outputs may be provided to indicate which sub-feeder is experiencing the worst insulation resistance. These are wired as per standard digital inputs:
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1) Set the RS485 "owner" to "Bender". This tells the SA380TX what type of device is attached to the RS485 port
TOUCHSCREEN - CONFIG TOOLMenu→Configuration→RS485
2) Create a "Bender" slave unit. The SA380TX needs to be explicitly told about devices attached to the RS485 port. Remember, only a single isometer may be connected at any one time.TOUCHSCREEN - CONFIG TOOL
Menu→Configuration→TX Slaves
3 ) Check that the "Slave" has been successfully created
The SA380TX will create additional slave channels representing the data obtained over the RS485 interface. The screen grab below shows these channels in the web-based configuration tool. They will also be visible in the real-time displays and historic data logs accessible via the touch-screen,
WEB CONFIG OF CHANNELS
4) Check that the isometer device is active:
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Additional alarm state changes may also be observed, but not if no fault condition exists.
Real Time Digital Screen:
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This screen is a poor indicator of connection status, as the state of the digital channels depends on the fault condition of the cables under test. Bender CONN DN should be clear.
Real Time Analogue Screen:
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This should show the present alarm levels, as well as the current resistance to earth reading obtained from the isometer. The value of the Bender Insulation channel must match the value displayed on the isometer display exactly.
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If no RS485 data is visible:
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4-20mA Setup
You will need to apply a polynomial mapping to translate the 4-20mA output from the Bender RK170 into a readable resistance.
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Simply click on the "name" field in the web-based configuration tool to rename the digital channels such that they match the feeder name (e.g UP, DOWN, BRANCH etc)
DIGITAL SCREEN SHOT
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Acquiring and Transmitting Data
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Use a simple absolute acquire on Change. Double-Click on each of the Bender ALARM1 and Bender ALARM2 channels in turn and enter the setting shown below:
CONFIG OF ALARM LEVELS
All Digital Channels
Simply select push-to-server for all physical and RS485 channels. This is achieved by ensuring the "Push to Server" tick-box is checked for digital channels you which to send to Centrix, as shown below
DIGITAL CONFIG
Live Insulation Resistance (4-20 mA or RS485)
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To counter this, the "relative" acquire on change method must be set on the logger. To do this requires the use of the "Rail Event" feature of the SA380TX.
1) Open the "Rail Events" Tab - This is where we can create all sorts of clever acquisition rules.
RAIL EVENT TAB
2) Create a new "Rail Event" - This sets up a new set of acquisition rules. It is OK for your Rail Event to errors at this stage.
CREATE NEW RAIL EVENT
3) Create the "Start Trigger" - We want to acquire data when the SA380TX boots up, and then whenever there is a significant change in insulation resistance. Whenever there is a +/-5% change in insulation resistance, a new acquisition is started. It is OK for your Rail Event to errors at this stage.
SET START TRIGGER
4) Tell the SA380TX what to Acquire - We want to keep acquiring insulation resistance values so long as they continue change. Every time the insulation resistance changes by another 5% of its prior value, we grab another sample. It is OK for your Rail Event to errors at this stage.
SET ACQUISITION
5) Set the end conditions - We don't need an "end trigger" we keep on acquiring samples so long as they continue to change. At some point though we want to barrel these samples up and send them to Centrix. This is why we put a time-out period of 1 minute in place.
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Your Rail Event should now have no errors.
END TRIGGER
SET END TRIGGER
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Always remember to set the config on the SA380TX before closing the web-page! |
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