Electricity + Control April 2018

ELECTRICAL PROTECTION + SAFETY

Monitoring Surge Protective Devices Intelligently Smart Diagnostics and Qualified Testing

Dipl.-Ing. Holger Heckler, Phoenix Contact GmbH & Co. KG, Blomberg, Germany

Applicable DIN standards demand the regular inspection of surge protective devices, and many users also want additional monitoring during operation.

Take Note!

SPDs are designed such that typical manmade or weather- related surge voltages or lightning currents do not lead to appreciable premature ageing of the devices. Monitoring SPDs is es- sential for high system availability. SPDs with smart mon- itoring functions can detect complex error states, therefore going far beyond the func- tion of a simple thermal monitoring system. The status information of SPDs can now be acquired conveniently and then displayed and processed throughout the system and between systems.

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B ut what options are there for monitoring, diagnostics, and the electrical testing of de- vices? To be able to react quickly to device overloads or failures, the status of surge protective devices is transmitted and evaluated throughout the system or between systems. Sensitive electronic devices are increasingly being installed in areas where high system availa- bility is required. Surge protective devices – iden- tified in the following as SPDs – are used as effec- tive protection against manmade surge voltages and against weather-related surge voltages and lightning currents. SPDs are designed such that typical manmade or weather-related surge voltages or lightning cur- rents do not lead to appreciable premature ageing of the devices. Frequent manmade surge voltages and high-energy lightning events can, however, lead to the SPDs themselves ageing prematurely. At the end of their service life, SPDs are automat- ically switched to a safe state and are normally disconnected from the protected circuit. To ensure high system availability, SPD ageing must be de- tected as early as possible – prematurely damaged SPDs should be replaced as part of a preventive maintenance program. Premature SPD ageing can be easily detected through ‘smart’ monitoring func- tions and qualified electrical testing. SPDs with simple status indicator Many SPDs are equipped with a simple status in- dicator. On varistor-based SPDs, for example, the temperature of the varistors is monitored, and the status of the thermal disconnect device is displayed on the front of the SPD. Thermal discon- nect devices are not just used in SPDs for energy technology applications. They can also be used in

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MCR or data-related applications, to detect over- loads in SPDs due to impermissibly high external voltages – for example through the unintentional connection of a higher voltage to a circuit with a lower dielectric strength. Smart status monitoring In SPDs for MCR and data-related applications, monitoring electronics integrated into the devices have been used increasingly in the last few years. Such ‘smart’ SPDs can measure leakage currents, detect short circuits and register surge voltages and lightning currents. Smart SPDs often need an auxiliary voltage sup- ply – 24 Vdc, for example. User-friendly SPDs are designed in such a way that the supply of auxiliary voltage and the acquisition of status information is possible without the need for additional wiring or configuration work – for example via a DIN-rail-in- tegrated bus system. SPDs are often equipped with remote indication contacts for transmitting status information. Users often want a group message to be issued if one or more SPDs are defective. A group message can be realized through the series connection of remote indication contacts. Some more techni- cally sophisticated SPDs enable the generation of optoelectronic group messages, for example. Here, Phoenix Contact offers its TERMITRAB complete product range, while the PLUGTRAB IQ product range is available for group messages via DIN-rail-integrated bus systems. In some cases, SPDs are installed in remote locations – for example in elevated water tanks, Acquiring and processing status infor- mation

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22 Electricity + Control

APRIL 2018