Advantages and disadvantages of microprocessor protection of electrical equipment

The control panels of modern electrical distribution substations, as well as reconstructed objects, are increasingly equipped with microprocessor-based protective devices... Modern achievements in the field of microprocessor technologies make it possible to create full-fledged devices that are in no way inferior and moreover, in many respects they surpass their ancestors — protective devices built on electromechanical relays.

Modern devices for relay protection based on microprocessors and equipment automation are characterized by many advantages. But, like any device, microprocessor protection also has its drawbacks. In this article, we will present their main advantages and disadvantages and conclude the importance of choosing microprocessor devices for the protection of electrical equipment.

Let's start with the benefits.The main advantage of microprocessor-based equipment protection terminals is their flexibility. In addition to the main functions, namely the application of equipment protection and the operation of automatic devices, microprocessor terminals measure electrical quantities.

If we look at the old protection panels of the substations, we see a lot of relays and analog meters. In the case of using microprocessor protection, there is no need to install additional measuring devices, since the values ​​of the main electrical quantities can be fixed at LSD display protection terminals.

Another advantage can be noted here — measurement accuracy. An analog device allows you to measure a value with a certain error, and if the devices serve for more than a dozen years (and most of the measuring devices of electrical installations are in this state), then their accuracy is significantly reduced and it is not always convenient to record the testimony.

The terminal display shows the exact values ​​of electrical quantities and, importantly, phase by phase. This makes it possible to monitor the open (closed) position of all breaker poles.

Based on the above, one more advantage of microprocessor-based protections can be distinguished — compactness. With the use of microprocessor technology, the total number of protection, automation and equipment control panels installed in the general control of the substation is literally halved.

If, for example, for protection, operation of automatic devices, control of switches of power transformers, three panels with electromechanical protections were installed, then in the case of using microprocessor protections, all the necessary functions are performed by two small terminals installed on one panel.

Another advantage is the convenience of troubleshooting. In case of deviations from the normal operation of the equipment, including in the event of an emergency, the LEDs of the protective terminal light up, signaling this or that event.

The operating personnel serving the electrical installation maintains a layout diagram (mnemonic diagram) that depicts the actual position of all switching devices, including stationary grounding devices. In this case, changing the position of the switching devices on the layout diagram is done manually.

Microprocessor protection terminals allow you to completely abandon the breadboard circuit. A simulated compartment diagram is shown on the safety terminal displays of each compartment, in which the positions of the switching devices are automatically changed according to their actual position.

In addition, all protective terminals are connected to SCADA system, which shows the entire substation diagram, load values ​​for each link, substation bus voltages, and real-time recording of emergency situations occurring.

Synchronization of SCADA systems of substations with a dispatch center allows the dispatcher on duty to register emergency situations in a timely manner, to control the switching process by the operational staff. Before issuing permission to allow the brigade to carry out planned work, the dispatcher on duty, thanks to the SCADA system, can personally check the correctness and sufficiency of the security measures taken.

Disadvantages of microprocessor terminals for equipment protection for electrical installations

A significant disadvantage of microprocessor devices is their high cost. In addition, significant enterprise costs are allocated to the maintenance of microprocessor devices: it is necessary to have expensive equipment, software, as well as specialists with appropriate qualifications.

The absence of expensive maintenance of microprocessor devices is not significant if all substations of the enterprise are equipped with modern microprocessor techniques. In this case, these devices are serviced by the relay protection and automation service, which specializes exclusively in these types of protection devices.

If microprocessor protections are installed at several sites, it is really costly to the enterprise, as it becomes necessary to maintain specialists from several services to service both microprocessor devices and traditional electromagnetic ones.

Another drawback microprocessor devices — narrow range of operating temperatures. Traditional protective devices based on conventional relays are quite unpretentious and can operate over a wide range of operating temperatures.At the same time, to ensure the correct operation of microprocessor devices, it is necessary to install additional air conditioning equipment.

It should be noted such a drawback of microprocessor devices as periodic errors in the software. Despite the statements of the manufacturers of microprocessor protections about their stable operation, an error in the operation of the software is very often observed (for example, periodically restarting the terminal). If a short circuit occurs during a software failure, it can lead to equipment damage because the connection is unprotected at that point.

Against the background of the numerous advantages of microprocessor devices, their disadvantages are not so significant and in some cases can be excluded. For example, installing reliable software and ensuring optimal operating conditions for microprocessor devices practically excludes the occurrence of errors or failures in their operation.

In conclusion, we can conclude that the introduction of microprocessor technologies in electric power enterprises is recommended and justified by many undeniable advantages.