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This project is about device for measuring transitional resistance between contacts of disconnectors, switch disconnectors and circuit breakers in transformer stations. Device is developed for and is especially useful during the transformer stations periodical checking when electrical power is completely disconnected (manual mode). Besides measuring transitional resistance, device can be used for thermal relays checking in transformer stations. Device is supplied by electrical power from automotive lead-acid battery 12V= (Cn=55Ah ). Setting of working parameters (reprogramming of stored programs) and data acquisition can be done by computer to which device have to be connected with special software (automatic mode). Regulated current range is from 0A to 100A=, with input voltage (battery voltage) of min. 10V and output voltage of max. 5V (voltage drop on testing contact).

The Programs

All tests programs can be split into steps, where certain operations must be executed under well defined conditions. Each step is fixed in a program line.

Each program step is divided into columns and each column has a headline describing its function.

Column explanations:

  • Column: Label
    • Each program step can be labeled which is used for controlling of program executing.
  • Column: Operation
    • Each program step starts with an operator determining the function of the test circuit. The operator names are simple abbreviations of the respective functions (charge, discharge, ramp, cycle, pause, stop).
  • Column: Set value
    • As nominal values for this step may be entered current, voltage or resistance of power values.
  • Column: Term. condition
    • The termination values current, voltage, time, capacity, energy and temperature determine the end of a program step and thus the beginning of the next program step. In building of condition can be used logical operators AND, OR, NOT.
  • Column: Term. action
    • Possibilities for The Term. Action columns are:
      • GOTO label -transfers program control to the specified program step
      • NEXT -goes to the next program step
      • STOP -terminates program
  • Column: Abort condition
    • The values entered under this column may be the same as for the termination values. However, in this case, the program run will be terminated if one of these limit values is reached.
  • Column: Registration
    • The conditions for the registration are entered into the last column. These may be time intervals or changes in current, voltage, capacity, energy or temperature.

Technical specifications:

Charge. current: Max 100A
Nominal battery voltage: 12V
Charge voltage range: 0-5V
Accuracy: 0,5% of set value
Power circuits: Transistors
Controlled characteristics: Constant current, voltage, power, resistance
Control elements: main switch, program selector switch, party line connection, start, stop, pause, automatic/manual buttons
Controlled variables: Current, voltage, power and resistance
Programmable functions: Charge, pause, cycles, cycles in cycles, "go to" steps
Termination values: Charge time, charge voltage, charge current, Ah charged, Wh charged, discharge time, final discharge voltage, discharge current, Ah discharged, Wh discharged
Display of measuring values: During operation permanently on the monitor of the host computer
Display: LED's for power, active, pause, program selected, digital instruments for current and voltage with additional test sockets

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