RU117734U1 - DEVICE FOR DYNAMIC DETECTION OF EMERGENCY ELECTRIC DISCHARGE - Google Patents

Abstract

1. A device for dynamic detection of an emergency electrical discharge containing a load current sensor of the monitored network with an input protection device connected to the output, the signal from which is fed to a broadband amplifier, from the output of which it is fed to an analog-to-digital converter, using which a discrete time reading is performed of the registered signal i (t) of the load current of the monitored network, the analog-to-digital converter is connected to a functional module - a digital logic device, with the help of which M samples im are obtained for the time interval Tj, then the set of samples obtained for the previous period is subtracted from the obtained set of samples time Tj-1:! ,! where im is the m-th element of the sample set obtained from the sampled load current signal read over the time interval Tj; ! M is the number of readings obtained during the time interval Tj; ! the obtained sets of samples are averaged using the averaging operator!,! where S is a fixed number of samples falling into the radius of a small neighborhood of τ; ! and calculate the norm of the result obtained by the formula:! ; ! to isolate high-frequency components, the averaging operator is applied to the initial set of samples im according to the formula:! ,! To increase the reliability of the estimate, slowly changing components of the sequence of samples of several periods of analysis are excluded: im, 3 is subtracted from the initial set of samples im, and then the norm of the resulting set of numbers is calculated:! ; ! then from the obtained values xn, 1, xn, 2 subtract the arithmetic mean values of the sets of samples xm, k, n�

Description

A utility model - a device for dynamic detection of emergency electric discharge - relates to protection devices in the field of electric power and fire safety, which automatically shut off and directly respond to an unacceptable deviation from normal electrical operating parameters with subsequent restoration of the connection or without it, namely, to dynamic detection devices emergency electrical discharge.

In electrical installations and cable lines, due to mechanical, chemical and temperature influences, insulation damage is formed, which leads to a violation of the functioning of the electrical circuit, a change in the set of characteristics corresponding to it and the emergence of emergency operating modes. The greatest difficulty in detection is emergency conditions, in which physical processes with electrical discharges occur.

A feature of modern electrical installations is the presence in them of devices with single or periodically repeating electrical discharges or devices that generate a current shape similar to the discharge current in normal operation. In this regard, when developing a device for the dynamic detection of emergency electrical discharge, it became necessary to distinguish it into two classes - a regular electrical discharge and emergency electrical discharge.

By standard electric discharge (SER) we mean a discharge of any kind - spark, arc, etc., inherent in a number of electrical machines and devices (collector motors, switches, contactors, relays, welding machines, discharge lamps, etc.). The regular electrical discharge can also include electrical processes occurring in a controlled network, which have a number of characteristics characteristic of the discharge - transient and switching processes that accompany the operation of switching power supplies and voltage converters, frequency drive devices, etc.

An emergency electric discharge (AER) will be considered a discharge of any kind - spark, arc, etc., which is not typical for electrical installations, machines and devices in good condition, which can lead to ignition or ignition of insulating materials and surrounding objects and substances.

Emergency electrical discharge, in turn, it is advisable to divide according to a number of signs and features of detection into three types: serial, parallel and AER to earth.

Serial emergency electrical discharge occurs when a reliable electrical contact is broken in the circuit with the connected load. The series emergency electrical discharge current is limited by the rated load current.

A parallel emergency electrical discharge occurs during arc or spark discharges between phase and (or) neutral conductors.

Emergency electrical discharge to earth is a special case of parallel emergency electrical discharge and occurs during arc or spark discharges between phase conductors and grounded parts of the electrical installation (protective earth conductor).

In an emergency, single spark discharges initially appear, characterized by an extremely short discharge current. The released heat at a sufficient frequency of occurrence of spark discharges contributes to carbonization of the insulating material and the flow of the emergency electric discharge into the next, more stable phase - the arc discharge. Similarly, the process develops when the electrical contact in the terminal blocks and other switching products is broken.

The share of fires resulting from unreliable contact and damage to 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, devices for protection against emergency electrical discharge are relevant and should be used on electrical installations of all categories, both industrial and domestic.

Existing protection devices using circuit breakers (AB) and residual current circuit breakers (RCD) do not allow timely shutdown of the damaged part of the electrical installation, therefore, to significantly increase the level of safety of electrical installations, the need arose to develop new devices.

The closest in its technical essence and the achieved result to the claimed utility model is a device [application for US patent 2009/0059449 A1, publ. 03/05/2009], in which the registered current signal of the controlled network is supplied to two independent channels; the first channel contains a high-pass filter (HPF), designed to remove from the signal of the main harmonic of the AC network, the second - a low-pass filter (LPF), which serves to suppress the high-frequency components of the current arising, in particular, during sparking. The current signals of each channel after filtering are digitized and processed using a microprocessor as follows. The signal of the first channel is analyzed to identify one or more statistical characteristics. The signal of the second channel is used to calculate the rms value of the load current. The statistical characteristics of the signal of the first channel are compared with certain ranges of values depending on the rms value of the load current. If the values of statistical characteristics fall within the limits specified for a certain value of the load current, the values of the logical counter increase. When the limit value is reached, a signal is generated leading to a blackout of the controlled network.

Significant disadvantages of this technical solution are: the possibility of false operation of the device during normal operation of loads with high inrush currents and a high level of regular electric discharges - collector motors and switching power supplies, failure to ensure fire safety in the presence of an emergency electric, including arc, discharge, which is one of types of emergency electrical discharge of low power, the dependence of the limit level of emergency electrical discharge Yes, from the load current of the controlled network, leading to an unacceptable increase in its threshold value, the impossibility of stable registration of short-term spark discharges.

The objective of the utility model - the device for dynamic detection of emergency electrical discharges - is to ensure stable operation and the absence of false alarms for all types of loads, including the presence of standard electrical discharges and inrush currents of any level, and to ensure a stable and constant threshold level of emergency electrical discharges, based on experimental data on the minimum discharge energy required for ignition, registration of both arc and spark elec richesky discharges.

To obtain such a technical result, a dynamic emergency electrical discharge detection device is proposed that contains a load current sensor of a controlled network with an input protection device connected to the output, the signal from which is fed to a broadband amplifier, from the output of which it is fed to an analog-to-digital converter, using which produce a time-discrete reading of the registered signal i (t) of the load current of the controlled network, an analog-to-digital converter for Module function for prison - digital logic device, which is obtained using samples M i _m in the interval of time T _j, set further from the obtained set of subtracted samples elementwise samples obtained during the previous time interval T _j-1:

,

where i _m is the m-th element of the set of reports obtained from the sampled signal of the load current, read over the time interval T _j ;

M is the number of samples obtained over a period of time T _j ; the obtained sets of samples are averaged using the averaging operator

,

where S is a fixed number of samples falling into the radius of a small neighborhood of τ;

and calculate the norm of the result by the formula:

;

to select high-frequency components, the averaging operator is applied to the initial set of samples i _m according to the formula:

,

To increase the reliability of the estimates, slowly varying components of the sequence of samples of several analysis periods are excluded: from the initial set of samples i _m, i _{m, 3 is} subtracted elementwise, and then the norm of the obtained set of numbers is calculated:

;

then from the obtained values x _{n, 1} , x _{n, 2, the} arithmetic mean values of the sets of samples x _{m, k} obtained for the last r time intervals T _j are subtracted and their absolute values are taken:

;

then, applying to each of the sequences of values of y _{n, 1} , y _{n, 2 a} transformation equivalent to a two-stage filtering scheme consisting of a nonlinear filter for suppressing isolated pulses and a linear accumulation filter:

;

Where ;

get the values of z _{n, 1} and z _{n, 2} and compare them with the given threshold values α and β, i.e. check the fulfillment of the condition:

(z _{n, 1} > α) & (z _{n, 2} > β),

if this condition is met, a signal is generated to turn off the electrical installation, which is fed from the output of the control and analysis unit to an indicator, the output of which is connected to a relay, which actuates the actuator acting on the contact group, by means of which the controlled network is de-energized.

The device can be structurally and functionally combined with a residual current device, and / or with a circuit breaker for protection against overloads and overcurrents.

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

Figure 1 shows a block diagram of a device.

Figure 2 - algorithm of the functional module of the device.

Figure 3 is a timing diagram of the operation of the device.

The device (Fig. 1) contains a contact group 2, a surge protection unit 3, a load current sensor 4, a power supply 7, an input protection device 9, an amplifier 11, an analog-to-digital converter 12, a functional module 14, an indicator 13, a relay 10 , an actuator 8 and, if combined with a protection device, thermal and electromagnetic releases, and a differential current sensor 6.

The device is connected to a controlled network in series with loads and 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 and to the electronic circuit of the device, to the load current sensor 4 and to the output terminals 5.

The signal from the load current sensor 4 is fed to the input protection device 9, which provides additional protection for the electronic circuitry of the device during prolonged overload (if the device does not include a circuit breaker or if it is damaged). Next, the signal is amplified by an amplifier 11 and fed to an analog-to-digital converter 12 for digitization and further processing using the functional module 14.

Functional module 14 contains a microcontroller or other digital logic device with additional elements that provide the desired mode of operation. With its help, they collect, store and process the digitized data of the current signal received from the sensor, generate a signal to the indicator 13 and commands to the relay 10 to actuate the actuator 8 in order to open the contact group 2 and disconnect the controlled network when an emergency occurs.

Functional module 14 processes the incoming signals and issues information messages or generates a command to shut down the monitored network according to the algorithm presented in Fig. 2 and includes a processor, a buffer, a counter, and random access memory.

Figure 3 shows a timing chart explaining the sequence of actions performed by the device.

When the device is turned on, it initializes, including resetting the time counter and buffer, setting the initial parameters (suppression and quieting parameters) and the analysis period T. At the same time, the counter starts counting, the recording of the current signal registered and digitized by an analog-to-digital converter in the form of codes in buffer, and their grouping occurs in frames.

The time counter counts throughout the frame (FRAME 1 in FIG. 3) until the start of the receipt of frame data following the current frame (FRAME 2).

At the end of the initialization process, the processor goes into standby mode (writing data to the buffer and counting time continue).

At the moment of the full filling of FRAME 1, the counter value becomes equal to the value of the analysis period T, then the data from the buffer is transmitted to the processor for further processing, the buffer is zeroed, the counter is reset to zero and the countdown continues until the value equal to the analysis period T is reached (end of FRAME 2).

After receiving data from the buffer, the processor initiates the processing of the current frame (FRAME 1) in the form of sequential calculations of three pairs of values of X ₁ and X ₂ , Y ₁ and Y ₂ , Z ₁ and Z ₂ , and after each calculation, the pairs of their values are stored in RAM for further use, as the calculation of each subsequent pair of values, according to the algorithm of FIG. 2, occurs recursively, through the values obtained during the processing of previous frames.

After calculating the last pair of Z ₁ and Z ₂ values per frame, which corresponds to the end of the processing by the processor of the data received for the previous frame, the condition (Z _{1, current} > α) & (Z _{2, current} > β) is checked and the processor goes into mode waiting (the processor stores pairs of values in RAM, recording or overwriting data in the buffer continues).

When the counter reaches the next value equal to the analysis period T (end of FRAME 2), the process is repeated similarly to the processing of FRAME 1: the FRAME 2 data from the buffer are transferred to the processor for processing, the buffer is reset or receives permission to overwrite the data stored in it, the counter is reset and continues to count time. After the processor calculates the next pairs of values of X ₁ and X ₂ , Y ₁ and Y ₂ , Z ₁ and Z ₂ , the current pairs are written to the place of the previous values, and the memory cells with the current pairs of values remain in storage mode until the next overwriting or general reset command .

The frame-by-frame processing process continues continuously until the condition (Z _{1, current} > α) & (Z _{2, current} > β), when verified by the processor _, becomes true.

When an emergency electric discharge occurs in the controlled network (Cadre 3 and Cadre 4 in Fig. 3 — the presence of random sharp peaks and dips on the current waveform), the value of the irregular component (IR) of the signal increases, which causes an increase in the value of Z ₂ , while the repeatability is disturbed waveform i.e. violation of the periodicity of the regular component (RC), leading to an increase in the value of Z ₁ evaluating the aperiodicity of the RC. Upon reaching Z ₁ and Z _{2 the} established threshold values cal, respectively, the condition:

(Z _{1, current} > α) & (Z _{2, current} > β)

takes the value:

(Z _{1, current} > α) & (Z _{2, current} > β) = TRUE,

the processor generates an alarm (ALARM in figure 3) and (or) generates a command (in the form of a signal to the executive node) to disable the monitored network.

As a result of the implementation of the inventive device, the reliability of determining an emergency electric discharge is significantly increased, false alarms are excluded with the simultaneous operation of loads of various types (purely active, inductive, capacitive and mixed). Separately, it should be pointed out that the device is operating at a high speed and that emergency situations are recorded steadily before the ignition of a stable electric arc, most often leading to a fire. This invention can be applied in networks of both alternating and direct current.

Thus, the implementation of the proposed device for dynamic detection of emergency electrical discharge provides a fire warning in case of a malfunction in the electrical network or electrical installation, increases the degree of protection of people, residential, industrial and other objects from the damaging effects of fires.

Claims (3)

1. A device for dynamic detection of an emergency electric discharge, comprising a load current sensor of a controlled network with an input protection device connected to the output, the signal from which is fed to a broadband amplifier, from the output of which it is fed to an analog-to-digital converter, using which a time-discrete reading is performed the registered signal i (t) of the load current of the monitored network, the analog-to-digital converter is connected to a functional module - a digital logic device count, by which is obtained i _m M samples in the time interval T _j, set further from the obtained set of subtracted samples elementwise samples obtained during the previous time interval T _j-1:

, where i _m is the mth element of the set of samples obtained from the discretized signal of the load current, read over the time interval T _j ; M is the number of samples obtained over a period of time T _j ; the obtained sets of samples are averaged using the averaging operator

, where S is a fixed number of samples falling into the radius of a small neighborhood of τ; and calculate the norm of the result by the formula:

; to select high-frequency components, the averaging operator is applied to the initial set of samples i _m according to the formula:

, To increase the reliability of the estimates, slowly varying components of the sequence of samples of several analysis periods are excluded: from the initial set of samples i _m, i _{m, 3 is} subtracted elementwise, and then the norm of the obtained set of numbers is calculated:

; then from the obtained values x _{n, 1} , x _{n, 2, the} arithmetic mean values of the sets of samples x _{m, k} obtained for the last r time intervals T _j are subtracted and their absolute values are taken:

; then, applying to each of the sequences of values of y _{n, 1} , y _{n, 2 a} transformation equivalent to a two-stage filtering scheme consisting of a nonlinear filter for suppressing isolated pulses and a linear accumulation filter:

; Where

; get the values of z _{n, 1} and z _{n, 2} and compare them with the given threshold values α and β, i.e. check the fulfillment of the condition: (z _{n, 1} > α) & (z _{n, 2} > β), if this condition is met, a signal is generated to turn off the electrical installation, which is fed from the output of the control and analysis unit to an indicator, the output of which is connected to a relay, which actuates the actuator acting on the contact group, by means of which the controlled network is de-energized. 2. The device according to claim 1 constructively and functionally can be combined with a residual current device. 3. The device according to claims 1 and 2 can be structurally and functionally combined with a circuit breaker for protection against overloads and overcurrents.