Solid State Mitigation Cells (SSMC, PCR, Polarization cell) are indispensable parts in terms of many functions such as static, AC current discharge of cathodically protected structures, safety grounding, and equipotential generation etc.
Checking whether these cells fulfill their functions before and after installation ensures that the system can be set up properly and the installed system can be operated correctly.
Below are some methods for testing Solid State Mitigation Cells. With these methods, an idea can be obtained as to whether the devices are working correctly.
The methods described herein are only basic methods that to give an idea of the state of the devices. It is recommended to contact the device manufacturer and / or service provider for exact results.
AC Discharge Performance
The AC Voltage accross the terminals of a Solid State Mitigation Cell is a function of both AC current flowing through and the internal resistance of the device. For example, if 50 A AC is measured using a clamp amperemeter thorugh a Solid State Mitigation Cell whose internal impedance is specified as 0.015 Ohm, the AC voltage that should be measured between the terminals of the device is;
AC Voltage = 50A x 0.015 Ohm = 0.75V AC
If the measured voltage is lower than this value, it should be considered that there is a measurement error or if the measurement value is much greater than this value, appropriate action should be taken considering that there is a measurement error, connection error or fault. This calculated value shows the lowest possible value in terms of AC discharge performance. This value shows the lowest AC voltage value that can be measured on the protected structure if the grounding resistance of the system is theoretically zero (0) ohms. The effect of grounding resistance with the increase of current flowing through the system will be added to this calculated value. As the resistance of the grounding system increases, the AC voltage on the protected structure will also increase.
DC Leakage Current
It is expected that the DC current value flowing to the ground should be very low in the system where a properly working polarization cell is connected. (<0.015 A) While the system is protected cathodically, a current higher than 0.015 A DC (see product sheet leakage current) should not be measured when a measurement is made with a mA DC clamp meter(or by other means of measurement) over one of the cables connected to the Solid State Mitigation Cells from the system. The measured current higher than this value may indicate that the threshold values of the device are not suitable for the system or it may be an indication of a damaged device.
Testing the Device by disconnecting from the System
Suspicious devices that cannot be measured while connected to the system or that are seen to flow DC current while in the system can be separated from the system by taking appropriate measures. In such a case, it can be tested for short circuits as follows:
Necessary grounding measures must be taken before the device is disassembled from the system.
First, the terminals of the device are briefly connected and separated by a cable. Than, the digital multimeter is placed in the resistance or diode measurement position and connected to the device terminals.
For a healthy Solid State Mitigation Cells, the Multi meter will show a short circuit when it is first connected, and after a short time (within 10-30 seconds) the measured value on the display will start to go up and the short circuit will disappear. If there is a continuous short circuit, it can be thought that there is a problem with the device.
Measurements in accordance with the manufacturer’s declarations in terms of AC discharge and leakage currents are an indication that the devices are working correctly. For accurate results, the instructions specified in the manufacturer’s description or user manuals must be followed.