NOVA PDC / RVM – 01
Apparatus for diagnosing transformers by the method of measuring polarization / depolarization currents (PDC) and by the method of return voltage (RVM)
The NOVA PDC / RVM 01 is designed to control the wetting degree of the insulation of power transformers and shunt ballasts in operation, using direct current polarization of the paper-oil dielectric assembly.
The measurement process involves the application of a DC voltage in the range of 200-2500V during Tc, followed by shorting the system during Td, which will lead to the discharge of accumulated charges and highlight the polar charges due to the presence of water molecules in the dielectric assembly.
Dimensions measured by the device:
- technical condition of the circuit breaker, charging time (Tc);
- download time (Td);
- return time (Tr);
- return voltage (Ur);
- excitation voltage.
Facilities offered by the hardware structure:
- visualization of the set data, of the measurement results, of the diagrams, of the parameters and of the instructions for the user; connecting or disconnecting the appliance to / from the power supply network;
- calling information about the operation of the device;
- setting the date and time when the measurements are made;
- activation of automatic measurement procedures;
- activation of special measurement procedures;
- leaving a measurement program at any time;
- selecting parameters, date, file identification name, screen contrast;
- command various functions and display them on the current screen;
- printing test reports for single measurements and for series of measurements;
- connection to PC (RS 232C serial interface), connection of the device to the object to be tested (connection for triaxial cable), connection of the device to the power supply by means of filters;
- inner short circuit protection;
- rejection of signals of 50 Hz and higher at the entrance to the device: minimum 60 dB.
Facilities offered by software programs:
- identification of the tested object (transformer, reactance coil, etc.) and display on the screen;
- identifying the date and place of the investigation and displaying it on the screen;
- identification of the investigated insulation (eg IT JT + T + m) and display on the screen;
- identifying the relative humidity of the environment during the investigation and displaying it on the screen;
- setting the test conditions and displaying them on the screen: charging voltage (Uc), charging time (Tc), Tc / Td ratio, maximum time (Trmax) until the return voltage reaches the maximum value (Urmax), process duration return voltage measurement (Ur), time steps when measuring return voltage;
- setting the working mode (in automatic mode the device allows the measurement and determination of the sizes Urmax, Tmax, dUr / dt for the following values of the automatically switched loading time: 0.020s, 0.050s, 0.100s, 0.200s, 0.500s, 1.00s, 2.00s, 5.00s, 10.00s, 20.00s, 50.00s, 100.00s, 200.00s, 500.00s, 1000.00s, 2000.00s, 5000.00s, under the conditions of setting a constant value for the Tc / Td ratio);
- setting the automatic operating mode to raise the diagram Ur = f (Tr) for a certain Tc / Td ratio; determining in automatic working mode the dependency Urmax = f (Tc), dUr / dt = f (Tc), Tvarf = f (Tc), for a certain ratio Tc / Td and presenting the results in the form of tables and / or graphs;
- setting the possibility to measure the insulation resistances at Tc = 15 s, Tc = 60s, Tc = 120 s, Tc = 250s, Tc = 500 s, Tc = 600s;
- self-testing of the device in terms of disruptive influences.