What is a Cutter? What is it for, how does it work and what types are there?

Circuit breaker is a switching equipment that can open and close the circuit in electrical power systems under normal operating conditions, and in case of fault, it can safely interrupt the current under abnormal conditions such as short circuit or overcurrent. This device, also called a circuit breaker, is one of the most critical elements of the network, especially in terms of energy continuity and equipment safety. Briefly, the answer to the question of what a cutter is; It is a protection and control equipment that separates the electrical circuit in a controlled manner when necessary and opens it very quickly when necessary with the command of the protection system.

It would be insufficient to answer the question of what a breaker is for by simply cutting off electricity. Because the duty of the breaker is not only to cut off the energy, but to do it at the right time, under the right condition and safely. It can open and close under load in normal operation, helps to disconnect the line safely during maintenance, and protects the system with the opening command from the relay in case of malfunction. Thus, transformers, cables, busbars, motors, generators and other equipment are protected from short circuit effects.

The working principle of the breaker is based on the controlled separation of moving and fixed contacts. When the circuit is closed, current flows through the contacts. When the opening command comes, the contacts are separated and an electric arc occurs during this separation. The main engineering value of the breaker is its ability to safely extinguish this arc. If the arc cannot be extinguished effectively, the circuit cannot be completely interrupted and serious thermal and dielectric stresses may occur on the equipment. For this reason, each breaker type shows different operating characteristics depending on the insulation and arc extinguishing medium it uses.

One of the most common types of breaker in medium voltage systems is the vacuum breaker. In vacuum breakers, the arc is extinguished within the vacuum breaking cell. Since the vacuum environment does not contain ionizable gas, it becomes difficult to maintain the arc and the cutting process becomes more controlled at the current zero crossing. That's why vacuum breakers; It is frequently preferred in MV cubicles, industrial facilities, distribution centers and applications requiring high switching numbers.

Another common type of breaker is the SF6 breaker. In this structure, SF6 gas is used for arc extinguishing and insulation. This type, which was very common in medium and high voltage applications in the past, has found wide use thanks to its strong insulation properties. However, when choosing a site, not only the habit but also the technical needs of the system, maintenance approach, environmental conditions and operating policy should be evaluated together.

A cutter and a separator are not the same equipment, and this difference is very important. While disconnectors are generally used to disconnect at no load, breakers are designed to switch on and off the load current and fault currents within certain limits. For this reason, there is protection and controlled on-off where there is a breaker; In the separator, visible separation and safety are at the forefront. In practice, considering these two pieces of equipment interchangeably may lead to serious operating and safety errors.

Breakers are not equipment that only works in case of malfunction. In daily operation, energizing, de-energizing, line transfer, maintenance maneuvers and some load management operations are carried out through breakers. In this respect, it is an integrated system element that works together with the breaker, protection relay, current-voltage transformers, busbar system and control circuits. Reliable operation of a cutter in the field requires not only being mechanically sound; It depends on the correct operation of the opening coil, closing coil, spring winding system, auxiliary contacts and relay command chain.

Breaker types can be classified according to voltage level, place of use and arc extinguishing environment. While compact switches, open type power breakers and miniature circuit breakers are seen on the low voltage side; On the medium voltage side, fixed or withdrawable vacuum breakers and, in some applications, SF6 breakers come to the fore. At high voltage levels, different design logics and field equipment come into play. Therefore, the word cutter alone refers to a wide product family.

When selecting a breaker, rated voltage, rated current, short circuit breaking capacity, short-term withstand current, mechanical life, electrical life, frequency of use, mounting type and cell structure should be evaluated together. For example, a breaker selected without determining the required breaking capacity according to the short circuit calculation made in the facility may not show the expected performance in the event of a fault. Likewise, choosing a solution with insufficient mechanical life in a system that is frequently maneuvered may cause operational problems in the long term.

Withdrawable or withdrawable breakers used in medium voltage cells provide significant advantages in terms of maintenance and testing. Thanks to the operating states of the breaker such as test position, service position and reserved position, both operational safety increases and maintenance processes are carried out in a more controlled manner. However, in these systems, mechanical interlocks, cell door interlock structures and their relationship with the earth separator must be designed correctly.

Breakers are the visible face of the protection system. The relay detects the fault, but the equipment that does the physical tripping is the breaker. Therefore, no matter how accurate the relay setting is, a breaker with a faulty trip coil or a mechanically jammed mechanism cannot provide the expected protection in the field. Likewise, unnecessary trips, auxiliary contact errors or closing circuit problems may also cause production loss and operating irregularities. So the role of the breaker is not only electrical but also operational.

On the maintenance and operation side, it is not enough to focus only on the main contacts on the breaker. Opening coil, closing coil, spring winding motor, energy storage mechanism, auxiliary contacts, mechanical indicators and control circuit connections should be evaluated as a whole. Especially in MV systems, the operation of the breaker should be considered together with other equipment in the cell; earth separator, current transformers, voltage transformers and protection relay chain should be handled together.

In summary, cutter; It is an indispensable equipment for safe switching, fault separation and operating continuity in electrical systems. Regardless of whether it is vacuum or SF6 type, fixed or withdrawable design, used at low or medium voltage level, its basic purpose is the same: to safely open the circuit when necessary and protect the system. If breaker selection, MV cubicle suitability, equipment evaluation according to short circuit level or operational safety of the existing system will be examined together in your facility. HV/MV testing, maintenance and repair, on the project side LV/MV/HV project design and consultancy and business processes SA operation responsibility It is possible to progress in integration with services.