SU890514A1 - Electric equipment protection device - Google Patents

Description

(54) DEVICE FOR ELECTRICAL INSTALLATION PROTECTION

I

The invention relates to electrical engineering and can be used for complex protection of various three-phase electrical installations.

During operation, electrical equipment is often in various emergency modes: overload, short circuit, incomplete phase or asymmetric modes, and the electric drive also requires protection from incomplete short circuit (braked rotor) and zero protection (as required by safety). As a rule, each type of protection is performed by an appropriate apparatus.

Devices are known that are used to protect against incomplete phase modes. Current protection is used to protect against overcurrents, and current protection against short circuits and current protection against overload 1 are distinguished.

The short-circuit current protection, avoiding inrush currents, cannot protect against overloads, and the overload protection works in conjunction with a time relay, which, having a fixed trigger, does not protect against short-circuiting at high shutter speeds.

or the equipment overload capacity is not used due to false alarms during transient overloads. Often, overload protection is performed using thermal relays, but due to the different thermal characteristics of the relay and the motor, it is unreliable. Other types of protection are performed similarly by various special devices. Creating complex protection by simply summing up the effects turns out to be economically inexpedient, and reliability is low.

10 protection leads to the output of up to 20% of electric motors.

The closest to that proposed by technical significance is a filter switch consisting of a filter in the order of alternation of phases and the executive body.

Claims (2)

15 If a voltage system with reverse phase rotation is applied to the indicated relay, it will be able to protect electrical installations from non-phase-phase modes. Such relays are called null relays. If 20 at the input of a null relay is applied a symmetrical voltage system, then the voltage at the terminals of the actuator is absent and the output signal does not change. The output signal does not change even if two or three phases are broken. The executive body will change its state only when the voltage (break) in one phase decreases. For reliable protection of electric motors, a high sensitivity of the device is required, provided by the use of a filter with a high power consumption of 2. However, even in this case, protection is provided only against an incomplete phase mode. High sensitivity is necessary because when a phase is lost in a running engine, the voltage at its terminals due to the emf induced in the disconnected phase does not drop to zero, but only decreases by about 10-15%. In addition, this relay does not protect against overloads when the engine overturns, from short circuits and from the drive self-starting when the disappeared voltage is restored. The purpose of the invention is to enhance the functionality and increase the reliability of protection. The goal is achieved by the fact that a device containing a filter of the phase sequence alternation, connected to the phases of the protected network, and the executive body, is introduced into the load current measuring transducer, the integrating element and the threshold element, the output of which is connected to the executive body, and its input to the output the filter is in the order of phase rotation and the current transducer through the integrator, and the current transducer is included in one of the phases of the protected network. The drawing shows a block diagram of a protection relay. The protection device contains a 1 phase order interleaved filter, a current measuring transducer 2, an integrating element 3, a threshold element 4 and an actuator 5. A three-phase voltage system is supplied to the input of the filter 1 connected in parallel with the load 6. The signal at the output of the filter arises when the symmetry of the voltage system is violated or when the voltage decreases in any of the phases. The current transducer 2 converts the load current 6 into a transverse voltage, which through the integrating link 3 enters the input of the threshold element 4. As a result, logical processing times are performed and the protection is selective, i.e., its speed becomes dependent on the character and the dangers of an accident. Under the influence of emergency signals, threshold element 4 is triggered and actuates the executive authority 5, which issues a command to turn off the electrical installation or a warning signal. The use of new elements — a current measuring transducer with an integrating element and a threshold element in conjunction with a FPCHF — makes it possible, through logical-temporal processing of information, to extend the functionality of the relay and provide protection against unbalance of supply voltages; protection against incomplete-phase modes (break 1, 2 or 3 phases); zero protection; protection against overheating when the rotor of the induction motor is inhibited; protection against single-phase short circuit; phase-to-phase protection; dependent time-current protection during technological overload; protection when the core of a closed cage rotor breaks or phase rotor unbalance at the same time, the protection has good energy indicators (power consumption is not more than 10 behind) and allows setting the response threshold with accuracy of 2-5%. Improving the reliability of protection provides a significant population-only effect by reducing repair costs. Formula of the Invention Protection Device for Electrical Installations Containing a Phase Sequence Filter, Connected to the Phases of the Protected Network, and the Executive Body, characterized in that , in order to extend the functionality and increase the reliability of protection, a load current measuring transducer, an integrating element and a threshold element, the output of which is connected to the Yelnia body, and its input - to the output of the filter in the order of phase rotation and the sensor current through the integrating element, and a current transformer included in one of the phases of the protected network. Sources of information taken into account in the examination 1. Lobashev G. I., Datskov I. I. Operation of electric motors and starting protection equipment. M., Rosselkhozizdat, 1972, p. 38 2. Manufacturer V. P. and others. Elements of devices for relay protection and automation of power systems and their design. M., “Higher School, 1974, p. 140-148. g P II rJU