CN217956678U - Motor leakage protection circuit under ground protection of chemical production TN-S system - Google Patents

Abstract

A motor leakage protection circuit under ground protection of a TN-S system in chemical production is characterized in that a motor M1 junction box power supply under ground protection of the TN-S system controls power input of a motor through a circuit breaker QF1 and a motor control contactor KM1, the motor M1 is grounded and is connected with a zero line N at the same time, a first current transformer CT1 is arranged below the motor control contactor KM1, a three-phase power line penetrates through the first current transformer CT1, two ends of the first current transformer CT1 are connected with an unbalanced current detection relay KA1, a grounding wire PE and a zero line N which are connected with a shell of the motor M1 penetrate through the second current transformer CT2, two ends of the second current transformer CT2 are connected with a leakage current detection relay KA2, and the unbalanced current detection relay KA1 and the leakage current detection relay KA2 jointly control leakage protection of the circuit breaker QF 1. Through the protective action of the unbalanced current detection relay KA1 and the leakage current detection relay KA2, the leakage protection with high sensitivity, stability and reliability is provided for the motor.

Description

Motor leakage protection circuit under ground protection of chemical production TN-S system

Technical Field

The utility model relates to a chemical industry safety technical field, especially a motor earth leakage protection circuit under chemical production TN-S system ground protection.

Background

Along with the increasing expansion of chemical production devices, power supply and utilization load devices are also larger and larger, especially the safety problem of power supply and utilization equipment is particularly outstanding, and an electric leakage protection device in a power distribution system is improved and reliable along with the application of a new technology, so that the normal work and personal safety of the electric equipment are guaranteed, and serious economic loss is avoided.

The 380V/220V power supply of the chemical production device applies a TN-S system grounding protection mode. Most chemical devices are in toxic, harmful, flammable, explosive and highly corrosive open-air environments, the grounding protection of electrical equipment is more important, and acid, alkali and corrosion prevention is required.

The low-voltage load of the chemical device is mostly the motor load, the shell of the neutral line equipment is connected with zero, and the neutral line is needed for overhauling a power supply and lighting equipment and is used as a protective zero line. The protection PE lines of all the equipment are generally reliably grounded on the site of the equipment for repeated grounding protection to prevent the neutral line from being broken due to reasons and the equipment from being electrified.

As shown in fig. 1, when a casing of a motor M1 is grounded in a single phase, the grounding current flow direction is as follows:

(1) Id1: phase line → motor case → N line → power supply neutral point; the size of Id1 depends on the resistance of the phase line, the resistance of the phase line and the motor shell, the resistance of the N line and the resistance of a grounding line of a power supply neutral point;

(2) Id2: phase line → motor casing → PE line → grounding body → earth → power supply neutral point; the size of Id2 depends on the resistance of the phase line, the resistance of the phase line and the motor shell, the resistance of the repetitive field grounding point, the ground resistance of the grounding main line and the grounding line resistance of the power supply neutral point.

The contact resistance is relatively stable, except that the resistances of the phase line and the motor housing are unstable and otherwise substantially unchanged.

If the air switch is tripped by single-phase grounding short-circuit current of the air switch at the power supply side, the air switch is extremely unreliable. Since the grounding current may not trip the power-side switch when a single-phase grounding occurs at the end of the line, the equipment enclosure will be in danger of being charged. If the ground resistance is 1 ohm and the ground current is 100 amps, the device housing will carry 100 volts, which, once touched by a person, is sufficient to render the person fatal.

Disclosure of Invention

The utility model aims to solve the technical problem that a motor earth leakage protection circuit under chemical production TN-S system ground protection is provided, for TN-S system ground protection motor under the chemical production provides reliable and stable earth leakage protection, prevents the incident.

In order to solve the technical problem, the utility model discloses the technical scheme who adopts is:

the utility model provides a motor earth leakage protection circuit under chemical production TN-S system ground protection, motor M1 terminal box power under TN-S system ground protection passes through the power input of circuit breaker QF1 and motor control contactor KM1 control motor, motor M1 ground connection is connected with zero line N simultaneously, be equipped with first current transformer CT1 below motor control contactor KM1, the three-phase power cord passes first current transformer CT1, first current transformer CT1 both ends are connected with unbalanced current detection relay KA1, it has earth connection PE and zero line N of being connected with motor M1 shell to run through in the second current transformer CT2, second current transformer CT2 both ends are connected with leakage current detection relay KA2, the leakage protection of circuit breaker QF1 is controlled by unbalanced current detection relay KA1 and leakage current detection relay KA2 jointly.

The leakage protection control circuit structure for controlling the circuit breaker QF1 by the unbalanced current detection relay KA1 and the leakage current detection relay KA2 is as follows:

normally closed switches of the unbalanced current detection relay KA1 and the leakage current detection relay KA2 and tripping coils of the circuit breaking switch QF1 are connected in series, two ends of a series circuit are connected with a control power supply, and the switch is disconnected when the tripping coils of the circuit breaking switch QF1 lose power.

The utility model provides a pair of motor earth leakage protection circuit under chemical production TN-S system ground protection, through unbalanced current detection relay KA1 and leakage current detection relay KA 2' S guard action, for the motor provides sensitivity height, reliable and stable earth leakage protection.

Drawings

The invention will be further described with reference to the following drawings and examples:

FIG. 1 is a schematic diagram of the motor wiring under the ground protection of the TN-S system of the present invention;

FIG. 2 is a schematic diagram of the leakage protection circuit of the motor of the present invention;

fig. 3 is the structure diagram of the leakage protection control circuit of the present invention.

In the figure: the motor M1, the circuit breaker QF1, the motor control contactor KM1, the first current transformer CT1, the second current transformer CT2, the unbalanced current detection relay KA1 and the leakage current detection relay KA2.

Detailed Description

As shown in fig. 1-3, a motor leakage protection circuit under ground protection of a chemical production TN-S system, a motor M1 junction box power supply under ground protection of the TN-S system controls power input of a motor through a circuit breaker QF1 and a motor control contactor KM1, the motor M1 is grounded and simultaneously connected with a zero line N, a first current transformer CT1 is arranged below the motor control contactor KM1, a three-phase power line passes through the first current transformer CT1, two ends of the first current transformer CT1 are connected with an unbalanced current detection relay KA1, a ground wire PE and a zero line N connected with a housing of the motor M1 penetrate through a second current transformer CT2, two ends of the second current transformer CT2 are connected with a leakage current detection relay KA2, and the unbalanced current detection relay KA1 and the leakage current detection relay KA2 jointly control protection of the circuit breaker QF 1.

The leakage protection control circuit structure for controlling the circuit breaker QF1 by the unbalanced current detection relay KA1 and the leakage current detection relay KA2 is as follows:

normally closed switches of the unbalanced current detection relay KA1 and the leakage current detection relay KA2 are connected in series with trip coils of the circuit breaker QF1, two ends of a series circuit are connected with a control power supply, and the switch is disconnected when the trip coils of the circuit breaker QF1 lose power.

(1) When the motor is earthed in a single phase, if the earth resistance of the motor is 4 ohms, and the action current of the leakage relay is set to 300 milliamperes, the voltage of the shell of the equipment is only 1.2 volts, namely 4 milliamperes 300mA, the voltage is safe for people and equipment, and when the device detects that the leakage current value reaches a specified value, the current relay acts, the switch trips, so that the equipment is protected better;

(2) The three-phase motor adopts a zero sequence or three-phase zero sequence mutual inductor connected with a current mutual inductor on each phase as unbalanced current protection relay protection, and the actual running condition of the motor can be judged by protecting the main loop of each motor.

Claims (2)

1. A motor leakage protection circuit under ground protection of a chemical production TN-S system is characterized in that: the motor M1 junction box power supply under the ground protection of the TN-S system controls the power supply input of the motor through the circuit breaker QF1 and the motor control contactor KM1, the motor M1 is grounded and simultaneously connected with a zero line N, a first current transformer CT1 is arranged below the motor control contactor KM1, a three-phase power line passes through the first current transformer CT1, two ends of the first current transformer CT1 are connected with the unbalanced current detection relay KA1, a ground wire PE and a zero line N connected with a shell of the motor M1 penetrate through the second current transformer CT2, two ends of the second current transformer CT2 are connected with the leakage current detection relay KA2, and the unbalanced current detection relay KA1 and the leakage current detection relay KA2 jointly control the leakage protection of the circuit breaker QF 1.

2. The motor leakage protection circuit under the ground protection of the chemical production TN-S system of claim 1, characterized in that the control circuit structure of the unbalanced current detection relay KA1 and the leakage current detection relay KA2 for controlling the leakage protection of the cut-off switch QF1 is:

normally closed switches of the unbalanced current detection relay KA1 and the leakage current detection relay KA2 are connected in series with trip coils of the circuit breaker QF1, two ends of a series circuit are connected with a control power supply, and the switch is disconnected when the trip coils of the circuit breaker QF1 lose power.

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