RU117686U1 - ELECTRICAL INSTALLATION PROTECTION DEVICE WITH EMERGENCY ELECTRIC ARC DETECTION FUNCTION - Google Patents

Abstract

The inventive utility model relates to devices in the field of electric power and fire safety and is intended to prevent fire and damage to cable lines and electrical components that occur during overloads, short circuits, leakage currents and ignition of an electric arc by de-energizing consumers. The technical task of the proposed device is to increase the reliability of determining the combustion process of a sequential, parallel electric arc and an arc to the ground in an electrical installation, to reduce false arc detections when working with non-resistive loads, in particular with collector motors, loads with pulsed sources and devices with high multiples of starting currents in relative to the nominal, as well as the ability to work in a network with a changing composition of the loads. To solve the technical problem, a device containing a load current sensor is connected to the output of the filter, the signal from which is fed to an amplifier with a half-wave rectifier, the output is connected to an integrating element, the input of which also receives a negative feedback signal, after which the signal at the output of the integrating the element is compared with the threshold using a comparator and, in case of exceeding, they send a signal to turn off the electrical installation to the actuating unit, a voltage sensor is introduced, connected to the fi to the liter, the signal from which is fed to the amplifier, the output of which is to an analog-to-digital converter, connected to the control and analysis unit by output; the signal of the load current sensor from the output of the amplifier with a half-wave rectifier is converted into voltage and fed to an analog-to-digital converter, the output also connected to a control and analysis unit, which is a digital logic device, by which the integration of signals proportional to the values of the current drops is analyzed groups of signals of adjacent impulses of current drops, measure the instantaneous voltage values of the network at the moments of occurrence of pulses of current drops and exclude pulses that do not correspond to the conditions of ignition of the electric arc, then the bias voltage proportional to the regular and periodic components of the signal of the current drops is subtracted from the obtained voltage value proportional to the current differential pulses, the obtained result is compared with the threshold value characteristic of a fire hazard situation during arc burning and, in if it is exceeded, they generate signals to turn off the electrical installation, which from the output of the control and analysis unit is fed to the indicator, as well as to the force the output of which is connected to a relay that drives the actuator acting on the contact group, by means of which the controlled electrical installation is de-energized. The device can be structurally and functionally combined with AB, while changing the algorithm of the device, and the built-in function of protection against overcurrents and short circuits is deactivated. The device can be structurally and functionally combined with an RCD, while changing the algorithm of the device, and the built-in function of protection against leakage currents is deactivated. An actuating unit can be excluded from the device, in this case, the control signal is supplied to the coil of the contactor, starter, or other external switching device. The proposed utility model is illustrated by the drawings of figures 1-3. Figure 1 presents a diagram of the inclusion of the device in the network. Figure 2 - structural diagram of the device. Figure 3 - algorithms of the control unit and analysis of the device. The device can be placed in the inlet or distribution boards (Fig. 1), structurally combined with plug sockets and load plugs (power consumers), performed in a separate housing. The device provides detection of an electric arc, overload and leakage current in networks and loads connected to its output terminals. Figure 1, a, b, c shows the load with an electric arc on the ground, parallel and sequential arc, respectively. The device comprises a surge protection unit 3, load current sensors 4, differential current 6 and voltage 5, a power supply 24, a signal processing unit B, an actuation unit A and is connected to the network in series with the controlled part of the electrical installation. The device operates as follows. The mains voltage is supplied to the input terminals 1, which then goes to the contact group 2, used to disconnect the load in case of an emergency, the surge protection unit 3, which prevents the passage of short-term surge surges to a controlled electrical installation, to a group of sensors 4-6 and to the output terminals 7. The signal from the load current sensor 4 is fed to a filter 9, which distinguishes the current differences characteristic of the arc burning process, is amplified by an amplifier 13 and summed with a signal from a voltage amplifier with escheniya 17, then fed to the ADC 18 for digitizing and further processing and analysis by the control unit 22. Signals voltage sensors 5 and 6, leakage current is processed similarly, except summing the bias voltage. The control and analysis unit 22 is a microcontroller or other digital logic device, with the help of which they collect, analyze signals from sensors, send alarm indication signals 21 and open contact group 2 using an actuator 8. The signal is preliminarily amplified by amplifier 16 to a level sufficient to operate the relay 12 of the actuator actuator 8. The operation of the control unit and analysis 22 is carried out according to certain algorithms (figure 3). The proposed technical solution differs from the known ones in that it additionally contains operations for comparing current drops with the range of voltage acceptable for ignition of the arc and an algorithm for adjusting the accumulation time of the differences for recording an unstable or low power arc.

Description

The inventive utility model relates to devices in the field of electric power and fire safety and is intended to prevent fire and damage to cable lines and electrical components that occur during overloads, short circuits, leakage currents and ignition of an electric arc by de-energizing consumers.

In electrical installations and cable lines of domestic and industrial facilities, due to poor-quality installation work, under the influence of temperature extremes, high humidity, and mechanical influences, insulating materials of cables and contact groups of switching devices — contactors, relays, switches and load sockets — are gradually degraded, lampholders, etc.), leading to the possibility of short circuits, leakage currents to the ground and ignition of the electric arc, the release of heat energy and, as a consequence, to increase the temperature of damaged elements, which in many cases leads to fire.

Protection devices against overcurrents, short circuits - circuit breakers (AB) and against leakage currents exceeding safe values - residual current devices (RCDs) - are widely known and are widely used in the electric power industry. These devices do not allow to detect and (or) turn off the electrical installation when an electric arc appears.

The proportion of fires arising from unreliable contact of electrical components that do not lead to short circuits and overloads reaches 80% [D. Pavlov Research and development of an intelligent intrinsic safety device for automation systems: dis. Cand. tech. Sciences: 05.13.05 Vladimir, 2006 RSL OD, 61: 06-5 / 3843, p. 12], therefore, the use of an electrical installation protection device with the function of detecting an emergency electric arc is advisable at industrial enterprises, especially at oil production, storage and transportation facilities and gas, mining, the operation of toxic and explosive substances, flour mills, elevators, other fire and explosive facilities for special, military and civil purposes and in everyday life.

The phenomenon of the appearance of an electric arc is explained by the formation of an ionized conduction site in places of poor contact. Arc burning on alternating current occurs with a periodic repetition of the ignition and extinguishing cycles.

There are three types of arc: sequential, parallel and an arc to the ground.

A sequential electric arc occurs when a reliable contact in the circuit with the connected load is broken. The series current is limited by the rated load current.

A parallel electric arc occurs during an arc short circuit between phase and (or) neutral conductors.

An arc to earth is a special case of a parallel arc and occurs during an arc short circuit between phase conductors and grounded parts of the electrical installation (protective earth conductor).

With stable combustion, a parallel arc can cause the overcurrent protection circuit breaker to trip, and an arc to the ground can cause an RCD to trip.

However, in most cases, the arc burning process is unstable, which makes it difficult to register with conventional network protection tools. In particular, it is impossible to detect a sequential arc with standard protective equipment (AB, RCD). For this purpose, a new generation of devices is needed.

A device is known [Russian patent RU 2159468 C1 7 G08B 17/06, G08B 25/10, publ. 06/20/2005], according to which the total electric current is measured at the input of the electric network. From the measured total current by filtering, a high harmonics signal is determined, determined by the transition resistance. The generated signal is amplified, rectified and accumulated over a set time. During the accumulation process, the value of the total signal is compared with a given level of comparison. Each comparison level is selected for the corresponding degree of fire hazard of the network. Depending on the magnitude of the accumulated signal corresponding to the achieved comparison level, a warning signal or a command to turn off the electrical network is generated.

The disadvantages of this device are the low reliability of detecting a sequential electric arc when used in electrical networks with a high switching frequency of loads, since a high harmonics signal is used as an informative indicator, which also appears when switching loads and the operation of collector motors; the impossibility of full compliance with the strictly specified limits of the degrees of fire hazard to the actual operating conditions of the electrical installation.

The closest in technical essence and the achieved result to the claimed utility model is a device [US patent 5,691,869, publ. 12/25/1997], comprising a current sensor, a signal processing unit and an actuating unit combined with a contact group of a circuit breaker; wherein the signal processing circuit includes low and high frequency filters, a half-wave rectifier, an integrating element, and a circuit that generates a bias voltage to reduce the likelihood of false alarms, which contains a leakage current sensor. The device responds to an increase in the current drop that accompanies each ignition of the arc, and the frequency of the drops; the absolute values of the amplitudes are summed over the set time interval, and, in case of exceeding the threshold value, the device turns off the electrical installation. The device also responds to overload, a short circuit in the network and to excess current leakage acceptable value.

This device is taken as a prototype.

Significant disadvantages of the prototype are the possibility of false arc detection during normal operation of loads with high inrush currents, inadequate fire safety in the presence of a low-power electric arc, erroneous detection of the arc and disconnection of the load during the operation of collector motors and switching power supplies, lack of registration of burning of the electric arc when connected inductive loads.

The technical task of the proposed device is to increase the reliability of determining the combustion process of a sequential, parallel electric arc and an arc to the ground in an electrical installation, to reduce false arc detections when working with non-resistive loads, in particular with collector motors, loads with pulsed sources and devices with high multiples of starting currents in relative to the nominal, as well as the ability to work in a network with a changing composition of the loads.

To solve the technical problem, a device containing a load current sensor is connected to the output of the filter, the signal from which is fed to an amplifier with a half-wave rectifier, the output is connected to an integrating element, the input of which also receives a negative feedback signal, after which the signal at the output of the integrating the element is compared with the threshold using a comparator and, in case of exceeding, they send a signal to turn off the electrical installation to the actuating unit, a voltage sensor is introduced, connected to the fi to the liter, the signal from which is fed to the amplifier, the output of which is to an analog-to-digital converter, connected to the control and analysis unit by output; the signal of the load current sensor from the output of the amplifier with a half-wave rectifier is converted to voltage and fed to an analog-to-digital converter, the output also connected to a control and analysis unit, which is a digital logic device, by which the integration of signals proportional to the values of the current drops is analyzed groups of signals of adjacent impulses of current drops, measure the instantaneous voltage values of the network at the moments of occurrence of pulses of current drops and exclude pulses that do not correspond to the conditions of ignition of the electric arc, then the bias voltage proportional to the regular and periodic components of the signal of the current drops is subtracted from the obtained voltage value proportional to the current differential pulses, the result is compared with a threshold value characteristic of a fire hazard situation during arc burning and, in if it is exceeded, they generate signals to turn off the electrical installation, which from the output of the control and analysis unit is fed to the indicator, as well as to the force the output of which is connected to a relay that drives the actuator acting on the contact group, by means of which the controlled electrical installation is de-energized.

The device can be structurally and functionally combined with AB, while changing the algorithm of the device, and the built-in function of protection against overcurrents and short circuits is deactivated.

The device can be structurally and functionally combined with an RCD, while changing the algorithm of the device, and the built-in function of protection against leakage currents is deactivated.

An actuating unit can be excluded from the device, in this case, the control signal is supplied to the coil of the contactor, starter, or other external switching device.

The proposed utility model is illustrated by the drawings of figures 1-3.

Figure 1 presents a diagram of the inclusion of the device in the network.

Figure 2 - structural diagram of the device.

Figure 3 - algorithms of the control unit and analysis of the device.

The device can be placed in the inlet or distribution boards (Fig. 1), structurally combined with plug sockets and load plugs (power consumers), performed in a separate housing. The device provides detection of an electric arc, overload and leakage current in networks and loads connected to its output terminals.

Figure 1, a, b, c shows the load with an electric arc on the ground, parallel and sequential arc, respectively.

The device comprises a surge protection unit 3, load current sensors 4, leakage current 6 and voltage 5, a power supply 24, a signal processing unit B, an actuation unit A and is connected to the network in series with the controlled part of the electrical installation.

The device operates as follows.

The mains voltage is supplied to the input terminals 1, which then goes to the contact group 2, used to disconnect the load in case of emergency, the surge protection unit 3, which prevents the passage of short-term surge surges to a controlled electrical installation, to a group of sensors 4-6 and to the output terminals 7.

The signal from the load current sensor 4 is fed to a filter 9, which distinguishes the current differences characteristic of the arc burning process, amplified and rectified using an amplifier with a half-wave rectifier 13 and summed with a signal from a bias voltage amplifier 17, after which it is fed to the ADC 18 for digitization and further processing the control and analysis unit 22. The signals of the voltage sensors 5 and the leakage current 6 are processed similarly, with the exception of summing with the bias voltage.

The control and analysis unit 22 is a microcontroller or other digital logic device, with the help of which they collect, analyze signals from sensors, provide signals for indicating an emergency situation 21 and open contact group 2 using an actuator 8. The signal is preliminarily amplified by an amplifier 16 to a level sufficient to operate the relay 12 of the actuator actuator 8.

The operation of the control unit and analysis 22 is carried out according to the following algorithms (Fig.3, a, b, c).

The algorithm for detecting an electric arc is presented in the form of a structural diagram in figure 3, a.

After the variables are initialized and the counters are reset from the load current sensors 4 (FIG. 2) and voltage 5, after filtering and amplification, signals proportional to the load current and the network voltage are received. Next, the current current difference is calculated as the absolute value of the signal increment between two adjacent samples.

Current. Delta = | Current. Report-Previous. Report. |

The difference is checked for belonging to the field of analysis, limited by the values of the mains voltage and the ignition (extinction) time of the emergency electric arc. In the case of going beyond the boundaries of the analysis area, the value of the differential is not taken into account. For one area of analysis, one maximum differential is remembered. Then, the differences are averaged over several areas of analysis. Differences that differ significantly from the average are not taken into account. The differences are summed over the accumulation time and form the accumulation value, which is compared with the limit value set during initialization. If the limit value is exceeded, a command is issued to turn off the electrical installation. If the value is lower than the limit, then the condition is checked for the analysis time exceeding the set value, and in case of exceeding, the analysis window is shifted along the time scale, and the accumulation value for the previous accumulation time interval is taken into account during the subsequent analysis and is reset. The bias signal is proportional to the regular and periodic component of the arc current. Subtracting the bias signal from the signal of subsequent drops from the load current sensor after filtering and amplifying it compensates for the effect of loads with a standard electric arc - collector motors - by adjusting the accumulation value. Depending on the conditions of the analysis, the accumulation value is reset, stored or changed. With a sufficiently low frequency of occurrence of signal drops, the accumulation time increases.

The detection algorithm for exceeding the maximum allowable value of the leakage current is presented in the form of a structural diagram in figure 3, b.

From the leakage current sensor 6 (figure 2) after filtering and amplification, a signal is proportional to the leakage current. After processing, the signal equivalent to the effective value of the leakage current is compared with the limit and, in case of excess, a trip command is issued.

The algorithm for detecting excess current load maximum value is presented in the form of a structural diagram in figure 3, c.

From the load current sensor 4 (figure 2) after filtering and amplification, a signal is proportional to the load current. After processing, the signal equivalent to the effective value of the leakage current is compared with the limit one and, in case of exceeding and working out the time delay, depending on the excess frequency and the set circuit breaker characteristic (B, C, D according to GOST R 50345-99), a trip command is given.

The device for detecting an emergency electric arc is used both as a separate unit, and combined with an AB, RCD or contactor (starter, relay) in various combinations.

When combined with AB, the function of monitoring the effective value of the load current and the actuating unit (using thermal and electromagnetic releases AB 23 are used), when combined with RCDs, the function of monitoring the effective value of the leakage current, leakage current sensor 6, filter 11, amplifier 15, ADC 20 and actuating unit, when using a contactor or other switch of the load current (starter, relay) exclude relay 12, actuator 8 and contact group 2 of the actuating unit, and the control signal from amplifier 16 is fed to the input outside his switch.

It is possible to use the device in a separate functional design as an additional element of electrical safety in the presence of AB and RCD in series connection.

The proposed technical solution differs from the known ones in that it additionally contains operations for comparing current drops with the range of voltage acceptable for ignition of the arc and an algorithm for adjusting the accumulation time of the differences for recording an unstable arc or low-power arc, which leads to a significant increase in the reliability of arc detection.

Claims (4)

1. An electrical installation protection device with an emergency arc detection function, comprising a load current sensor, to the output of which a filter is connected, the signal from which is fed to an amplifier with a half-wave rectifier, connected to an integrating element, the input of which also receives a negative feedback signal, after why the signal at the output of the integrating element is compared with a threshold using a comparator and, in case of exceeding, a shutdown signal of the electrical installation is fed to the actuator Leach in that the device is further installed a voltage sensor connected to the filter output signal from which is fed to an amplifier, the output of which - to an analog-digital converter, the output connected to the control and analysis unit; the signal of the load current sensor from the output of the amplifier with a half-wave rectifier is converted to voltage and fed to an analog-to-digital converter, the output also connected to a control and analysis unit, which is a digital logic device, by which the integration of signals proportional to the values of the current drops is analyzed groups of signals of adjacent impulses of current drops, measure the instantaneous voltage values of the network at the moments of occurrence of pulses of current drops and exclude pulses that do not correspond to the conditions of ignition of the electric arc, then the bias voltage proportional to the regular and periodic components of the signal of the current drops is subtracted from the obtained voltage value proportional to the current differential pulses, the result is compared with the threshold value characteristic of a fire hazard situation during arc burning, and if it is exceeded, they generate signals to turn off the electrical installation, which from the output of the control and analysis unit is fed to the indicator, as well as to the force the output of which is connected to a relay that drives the actuator acting on the contact group, by means of which the controlled electrical installation is de-energized. 2. The electrical installation protection device with the emergency arc detection function according to claim 1 is structurally and functionally combined with an overcurrent protection circuit breaker (AB). 3. The electrical installation protection device with the emergency arc detection function according to claim 1 is structurally and functionally combined with a residual current device (RCD). 4. The electrical installation protection device with the emergency arc detection function according to claim 1 is structurally and functionally combined with a contactor (starter, relay).