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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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The diagram on the left shows direct connection. Please consult the Bender user guide for exact terminations. Note that if the isometer is built into a Network Rail style cubicle arrangement, the "common" VFC connection is brought-out at the base of the cubicle through the terminal block position 37. The 12 individual feeder alarm signals are presented on terminal 38 (Feeder 1) through to 49 (Feeder 12). This is shown on the right |
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Channel Configuration & Commissioning
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Always remember to set the config on the SA380TX before closing the web-page, or touch-screen dialog box! Your changes won't take effect otherwise! |
Initial Setup
RS485 Setup
These steps may be completed on the SA380TX touchscreen, or via web-based configuration tool.
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 TOOLMenu→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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COMING SOON - REAL-TIME ANALOGUE DATA
Digital
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Setup
You will need to name any digital channels that derive from the fault evaluator unit.
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)
Setting the Acquisition
This requires connection via laptop
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Acquiring and Transmitting Data
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To perform the steps described in this section requires the use of the web-based configuration tool. The touchscreen interface is not sophisticated enough |
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Analogue Alarm Levels
Use a simple absolute acquire on Change:
TOUCHSCREEN - CONFIG TOOL
. Double-Click on each of the Bender ALARM1 and Bender ALARM2 channels in turn and enter the setting shown below:
All Digital Channels
Simply select push-to-server for all physical and RS485 channelsLive Insualtion Resistance. 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
Live Insulation Resistance (4-20 mA or RS485)
Standard acquire-on-change will grab incoming data based on on absolute change. This is not desirable when taking insulation resistance readings, as an absolute change of 10 k Ohm from 1 M Ohm to 990 k Ohm will happen very frequently, due to wet weather for instance, and not warrant any corrective actions, where . Whereas a change from 55 k Ohm to 45 k Ohm would cross an alert boundary and warrant immediate corrective action.
Setting a small acquisition threshold will cause a large amount of not very useful data to be captured, whereas setting a large threshold would cause low data volumes, but reduce sensitivity to genuine fault conditions.
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
CREATE NEW RAIL EVENT
SET START TRIGGER
SET ACQUISITION
SET END TRIGGER
Set the config.
1) Open the "Rail Events" Tab - This is where we can create all sorts of clever acquisition rules.
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.
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.
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.
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.
After 1 minute acquisition will end, and all samples acquired since the start trigger event will be sent to Centrix. Don't worry though, next time Insulation resistance changes by 5%, a brand-new acquisition will be triggered and the whole process repeats.
Your Rail Event should now have no errors.
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Always remember to set the config on the SA380TX before closing the web-page! |