CN109254206B - High-impedance electrical parameter on-line monitoring device and method - Google Patents
High-impedance electrical parameter on-line monitoring device and method Download PDFInfo
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- CN109254206B CN109254206B CN201811240374.5A CN201811240374A CN109254206B CN 109254206 B CN109254206 B CN 109254206B CN 201811240374 A CN201811240374 A CN 201811240374A CN 109254206 B CN109254206 B CN 109254206B
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- 230000007935 neutral effect Effects 0.000 claims abstract description 66
- 238000012544 monitoring process Methods 0.000 claims abstract description 36
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 230000002159 abnormal effect Effects 0.000 abstract description 2
- 238000012545 processing Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2688—Measuring quality factor or dielectric loss, e.g. loss angle, or power factor
- G01R27/2694—Measuring dielectric loss, e.g. loss angle, loss factor or power factor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/001—Measuring real or reactive component; Measuring apparent energy
- G01R21/002—Measuring real component
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/001—Measuring real or reactive component; Measuring apparent energy
- G01R21/003—Measuring reactive component
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Measurement Of Resistance Or Impedance (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
The invention discloses a high-impedance electrical parameter online monitoring device which comprises a voltage transformer, a current transformer, a neutral point CT measuring unit, a high-impedance online monitoring on-site unit, a data acquisition unit and a monitoring host; the on-line monitoring device disclosed by the invention utilizes the voltage transformer and the neutral point current transformer to comprehensively calculate and obtain the fundamental component of the instantaneous value of the high-resistance terminal voltage, further calculate the loss ratio and the inductance value which can accurately measure the high-resistance current state, and according to the loss ratio and the inductance value, the possible short circuit is detected and an alarm is provided; once the monitored high anti-loss ratio and the inductance value are abnormal, an operator on duty can immediately receive the alarm signal so as to accurately formulate a proper treatment scheme and reduce faults and losses in power operation.
Description
Technical Field
The invention relates to the field of circuit equipment, in particular to a high-impedance electrical parameter on-line monitoring device and method.
Background
At present, most ultrahigh voltage and extra-high voltage substations are provided with oil-immersed parallel reactors, and the oil-immersed parallel reactors are directly connected in parallel to the primary side of a main transformer and are commonly called as high reactance.
Because the high reactance is directly connected in parallel with the primary side of the main transformer, the voltage is very high, and the high reactance and the main transformer share a group of circuit breakers, once serious faults occur in the high reactance, the circuit breakers can trip immediately, large-area power failure accidents are caused, and even the safety of the whole power grid is endangered. Therefore, the high-resistance intelligent power supply system can perform real-time on-line monitoring, send out alarm signals in early accidents, and perform planned power failure maintenance, and has great significance in improving the power supply reliability and ensuring the safety of a power grid.
The high resistance can cause various faults, wherein the most serious is that the internal pressure of the high resistance is sharply increased to exceed a specified upper limit value, the pressure release device acts, oil and gas in the oil tank are sprayed outwards from the pressure release device, a micro switch on the pressure release device starts the circuit breaker to trip, and the main transformer is out of operation.
The reason for the high-resistance pressure release device action is generally that the high-resistance coil has turn-to-turn short circuit faults, the temperature of the short circuit ring rises rapidly in a short time, transformer oil in contact with the short circuit ring is heated, cracked and gasified, and at the moment, the pressure in the high-resistance oil tank rises rapidly, so that the pressure release device action is triggered.
The high reactance coil has a point in which an inter-turn short circuit occurs, the reactor becomes a virtual autotransformer, and the transformation ratio of the autotransformer is extremely large, the number of turns on the high voltage side is approximately equal to the number of turns of the reactor, the low voltage side has only one turn, and the low voltage side is in short circuit operation. The principle of ampere-turn balance shows that the current at the low-voltage side is extremely large, so that the huge heating power generated by the large short-circuit current in the short-circuit loop can crack and gasify part of oil in the reactor in a short time, and the pressure release device is caused to act.
In order to avoid the sudden failure of the high resistance when operators are unknowing and cause tripping of the main transformer, the health state of the high resistance needs to be monitored on line. Theoretically, as long as the instantaneous value of the terminal voltage of a single-phase reactor in operation and the instantaneous value of the current passing through the reactor can be collected, the reactive power (capacity), the active power (loss), the loss ratio and the inductance value of the reactor can be calculated, and if the reactor has a turn-to-turn short circuit fault, the loss ratio is higher than the rated value, and the inductance value is smaller than the rated value.
But the practical problems are:
(a) At present, most of high-reactance neutral points are grounded through small reactance, namely, neutral points of A phase, B phase and C phase of a group of reactors are connected to an inlet end of the small reactance, and an outlet end of the small reactance is directly grounded, so that voltage of each phase of the group of reactors cannot be directly calculated through secondary side voltage of a voltage transformer. Because the terminal voltage of each reactor is uncertain, the actual operation parameter of each reactor is unknown, and even if a certain reactor has turn-to-turn short circuit fault, the actual operation parameter cannot be known by a method of measuring the electrical parameter.
(B) Because the magnetic permeability of the transformer core is nonlinear and has saturation problem, the no-load current contains about 60% of third harmonic, and secondly, a large number of other harmonic sources exist in the system, so that the system voltage contains harmonic components; the current through the reactor contains harmonic components due to non-linearity of the reactor's own impedance and system voltage distortion factors.
For the above reasons, even if the terminal voltage instantaneous value and the current instantaneous value of the reactor can be acquired, the instantaneous values are not sine waves, and the instantaneous values are directly used for calculating the parameters of the reactor, so that larger deviation is caused, and the device is prevented from reporting or is prevented from reporting by mistake.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-impedance electrical parameter on-line monitoring device and method, which can accurately monitor the loss ratio and inductance value of high impedance, provide early warning at the early stage of short circuit of the high impedance, and reduce circuit faults and losses.
In order to solve the technical problems, the invention adopts the following technical scheme: the high-impedance electrical parameter on-line monitoring device comprises a voltage transformer, a current transformer, a neutral point CT measuring unit, a high-impedance on-line monitoring on-site unit, a data acquisition unit and a monitoring host;
The voltage transformer and the current transformer are connected into a bus circuit, and for a three-phase circuit, the voltage transformer generally needs to comprise an A-phase voltage transformer, a B-phase voltage transformer and a C-phase voltage transformer, and the current transformer comprises an A-phase current transformer, a B-phase current transformer and a C-phase current transformer;
The neutral point current transformer is connected with the neutral point small reactance, one end of the primary side of the neutral point current transformer is connected with the outlet end of the neutral point small reactance, and the other end of the primary side of the neutral point current transformer is directly grounded;
the neutral point CT measuring unit collects current instantaneous values of the secondary side of the neutral point current transformer and performs FFT (fast Fourier transform) on the current instantaneous values to obtain neutral point current instantaneous value fundamental components, and the neutral point CT measuring unit transmits the neutral point current instantaneous value fundamental components to the high reactance online monitoring local unit;
the high reactance on-line monitoring local unit calculates the fundamental wave component of the neutral point voltage instantaneous value by utilizing the fundamental wave component of the neutral point current instantaneous value and the reactance value of the neutral point small reactance;
the high reactance on-line monitoring local unit collects the voltage instantaneous value of the secondary side of the voltage transformer and performs FFT conversion on the voltage instantaneous value to obtain a voltage transformer voltage instantaneous value fundamental component, and the voltage transformer voltage instantaneous value fundamental component is used for subtracting the neutral point voltage instantaneous value fundamental component to obtain a high reactance terminal voltage instantaneous value fundamental component;
the high-impedance on-line monitoring local unit collects the instantaneous value of the secondary side current of the current transformer and performs FFT conversion on the instantaneous value to obtain the fundamental component of the instantaneous value of the high-impedance current;
The high reactance on-line monitoring local unit calculates reactive power, active power, loss ratio and inductance value of high reactance by utilizing the fundamental component of the high reactance terminal voltage instantaneous value and the fundamental component of the high reactance current instantaneous value, and transmits the calculation result to the data acquisition unit;
The data acquisition unit stores reactive power, active power, loss ratio and inductance value with high reactance and transmits the loss ratio and inductance value to the monitoring host;
the monitoring host compares the loss ratio with a loss ratio rated value, compares the inductance value with an inductance rated value, and controls the alarm device to send out an alarm if the difference value of the loss ratio and the loss ratio rated value is larger than a loss threshold value or the difference value of the inductance value and the inductance rated value is larger than an inductance threshold value.
The invention also provides a high-impedance electrical parameter on-line monitoring method, which is characterized by comprising the following steps:
Step 1: connecting a voltage transformer and a current transformer into a bus circuit;
step 2: a neutral point current transformer is connected to a neutral point small reactance;
Step 3: collecting the current instantaneous value of the secondary side of the neutral point current transformer and performing FFT (fast Fourier transform) on the current instantaneous value to obtain the fundamental component of the neutral point current instantaneous value;
Step 4: calculating the fundamental component of the neutral point voltage instantaneous value by utilizing the fundamental component of the neutral point current instantaneous value and the reactance value of the neutral point small reactance;
Step 5: collecting the instantaneous value of the secondary side voltage of the voltage transformer and performing FFT (fast Fourier transform) on the instantaneous value to obtain the fundamental component of the instantaneous value of the voltage transformer;
Step 6: subtracting the neutral point voltage instantaneous value fundamental component from the voltage transformer voltage instantaneous value fundamental component to obtain a high reactance terminal voltage instantaneous value fundamental component;
step 7: collecting the instantaneous value of the secondary side current of the current transformer and performing FFT (fast Fourier transform) on the instantaneous value to obtain the fundamental component of the instantaneous value of the high-resistance current;
step 8: calculating reactive power, active power, loss ratio and inductance value of the high reactance by using the fundamental component of the high reactance terminal voltage instantaneous value and the fundamental component of the high reactance current instantaneous value;
Step 9: and comparing the loss ratio with a loss ratio rated value, comparing the inductance value with an inductance rated value, and if the difference value of the loss ratio and the loss ratio rated value is larger than a loss threshold value or the difference value of the inductance value and the inductance rated value is larger than an inductance threshold value, sending out an alarm by using an alarm device.
The beneficial effects are that: the on-line monitoring device and the on-line monitoring method of the invention utilize the voltage transformer and the neutral point current transformer to comprehensively calculate and obtain the fundamental wave component of the instantaneous value of the high-resistance end voltage, further calculate the loss ratio and the inductance value which can accurately measure the high-resistance current state, and according to the loss ratio and the inductance value, the possible short circuit is detected and the alarm is provided; once the monitored high anti-loss ratio and the inductance value are abnormal, an operator on duty can immediately receive an alarm signal, and the operator on duty can inform a dispatching and superior lead and a reactor manufacturer according to relevant fault processing file regulations while paying close attention to the high anti-loss ratio so as to accurately formulate a proper processing scheme. On the other hand, the high-resistance loss ratio and the inductance value are stored by the data acquisition unit, and the internal software can conveniently output a chart and a curve by utilizing the historical data, so that the working data of the high resistance can be recorded all weather, and a worker can conveniently and timely call the data to research the reason for the generation of the high-resistance fault.
Drawings
Fig. 1 is a schematic structural diagram of an on-line monitoring device for high-impedance electrical parameters in embodiment 1.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments.
Example 1
As shown in fig. 1, the high-impedance electrical parameter on-line monitoring device of the embodiment comprises a voltage transformer, a current transformer, a neutral point CT measuring unit, a high-impedance on-line monitoring local unit, a data acquisition unit, a monitoring host and an alarm device;
The voltage transformer and the current transformer are connected into a three-phase bus circuit; the voltage transformer comprises an A-phase voltage transformer, a B-phase voltage transformer and a C-phase voltage transformer, and the current transformer comprises an A-phase current transformer, a B-phase current transformer and a C-phase current transformer;
The neutral point current transformer is connected with the neutral point small reactance, one end of the primary side of the neutral point current transformer is connected with the outlet end of the neutral point small reactance, and the other end of the primary side of the neutral point current transformer is directly grounded;
The neutral point CT measuring unit is connected with the neutral point current transformer and the high-impedance on-line monitoring on-site unit, the high-impedance on-site unit is connected with the data acquisition unit, and the data acquisition unit is connected with the monitoring host.
The working flow of the high-impedance electrical parameter on-line monitoring device of the embodiment is as follows:
(1) The neutral point CT measuring unit collects current instantaneous values of the secondary side of the neutral point current transformer and performs FFT (fast Fourier transform) on the current instantaneous values to obtain neutral point current instantaneous value fundamental components, and the neutral point CT measuring unit performs A/D (analog-to-digital) conversion on the neutral point current instantaneous value fundamental components and then transmits the neutral point current instantaneous value fundamental components to the high impedance on-line monitoring local unit;
(2) The high reactance on-line monitoring local unit calculates the fundamental wave component of the neutral point voltage instantaneous value by utilizing the fundamental wave component of the neutral point current instantaneous value and the reactance value of the neutral point small reactance;
(3) The high reactance on-line monitoring local unit collects the voltage instantaneous value of the secondary side of the voltage transformer and carries out FFT conversion on the voltage instantaneous value to obtain the fundamental component of the voltage instantaneous value of the voltage transformer;
(4) The high reactance online monitoring local unit obtains a high reactance terminal voltage instantaneous value fundamental component by subtracting a neutral point voltage instantaneous value fundamental component from a voltage transformer voltage instantaneous value fundamental component;
(5) The high-impedance on-line monitoring local unit collects the instantaneous value of the secondary side current of the current transformer and performs FFT conversion on the instantaneous value to obtain the fundamental component of the instantaneous value of the high-impedance current;
(6) The high-reactance on-line monitoring on-site unit calculates high-reactance reactive power, active power, loss ratio and inductance value by utilizing the high-reactance terminal voltage instantaneous value fundamental component and the high-reactance current instantaneous value fundamental component, and the high-reactance on-site unit transmits the calculated reactive power, active power, loss ratio and inductance value to the data acquisition unit;
(7) The data acquisition unit stores reactive power, active power, loss ratio and inductance value of each high reactance and transmits the data to the monitoring host;
(8) The monitoring host compares the loss ratio with the loss ratio rated value, compares the inductance value with the inductance rated value, and triggers an alarm device if the difference between the loss ratio and the loss ratio rated value is larger than a loss threshold value or the difference between the inductance value and the inductance rated value is larger than an inductance threshold value (the specific type of the alarm device is freely selected and configured according to the actual application requirements).
Although embodiments of the present invention have been described in the specification, these embodiments are presented only, and should not limit the scope of the present invention. Various omissions, substitutions and changes in the form of examples are intended in the scope of the invention.
Claims (2)
1. An on-line monitoring device for high-resistance electrical parameters is characterized in that: the system comprises a voltage transformer, a current transformer, a neutral point CT measuring unit, a high-impedance on-line monitoring on-site unit, a data acquisition unit and a monitoring host;
The voltage transformer and the current transformer are connected to the bus circuit;
The neutral point current transformer is connected with a neutral point small reactance;
the neutral point CT measuring unit collects current instantaneous values of the secondary side of the neutral point current transformer and performs FFT (fast Fourier transform) on the current instantaneous values to obtain neutral point current instantaneous value fundamental components, and the neutral point CT measuring unit transmits the neutral point current instantaneous value fundamental components to the high reactance online monitoring local unit;
the high reactance on-line monitoring local unit calculates the fundamental wave component of the neutral point voltage instantaneous value by utilizing the fundamental wave component of the neutral point current instantaneous value and the reactance value of the neutral point small reactance;
the high reactance on-line monitoring local unit collects the voltage instantaneous value of the secondary side of the voltage transformer and performs FFT conversion on the voltage instantaneous value to obtain a voltage transformer voltage instantaneous value fundamental component, and the voltage transformer voltage instantaneous value fundamental component is used for subtracting the neutral point voltage instantaneous value fundamental component to obtain a high reactance terminal voltage instantaneous value fundamental component;
the high-impedance on-line monitoring local unit collects the instantaneous value of the secondary side current of the current transformer and performs FFT conversion on the instantaneous value to obtain the fundamental component of the instantaneous value of the high-impedance current;
The high reactance on-line monitoring local unit calculates reactive power, active power, loss ratio and inductance value of high reactance by utilizing the fundamental component of the high reactance terminal voltage instantaneous value and the fundamental component of the high reactance current instantaneous value, and transmits the calculation result to the data acquisition unit;
The data acquisition unit stores reactive power, active power, loss ratio and inductance value with high reactance and transmits the loss ratio and inductance value to the monitoring host;
the monitoring host compares the loss ratio with a loss ratio rated value, compares the inductance value with an inductance rated value, and controls the alarm device to send out an alarm if the difference value of the loss ratio and the loss ratio rated value is larger than a loss threshold value or the difference value of the inductance value and the inductance rated value is larger than an inductance threshold value.
2. The high-impedance electrical parameter on-line monitoring method is characterized by comprising the following steps of:
Step 1: connecting a voltage transformer and a current transformer into a bus circuit;
step 2: a neutral point current transformer is connected to a neutral point small reactance;
Step 3: collecting the current instantaneous value of the secondary side of the neutral point current transformer and performing FFT (fast Fourier transform) on the current instantaneous value to obtain the fundamental component of the neutral point current instantaneous value;
Step 4: calculating the fundamental component of the neutral point voltage instantaneous value by utilizing the fundamental component of the neutral point current instantaneous value and the reactance value of the neutral point small reactance;
Step 5: collecting the instantaneous value of the secondary side voltage of the voltage transformer and performing FFT (fast Fourier transform) on the instantaneous value to obtain the fundamental component of the instantaneous value of the voltage transformer;
Step 6: subtracting the neutral point voltage instantaneous value fundamental component from the voltage transformer voltage instantaneous value fundamental component to obtain a high reactance terminal voltage instantaneous value fundamental component;
step 7: collecting the instantaneous value of the secondary side current of the current transformer and performing FFT (fast Fourier transform) on the instantaneous value to obtain the fundamental component of the instantaneous value of the high-resistance current;
step 8: calculating reactive power, active power, loss ratio and inductance value of the high reactance by using the fundamental component of the high reactance terminal voltage instantaneous value and the fundamental component of the high reactance current instantaneous value;
Step 9: and comparing the loss ratio with a loss ratio rated value, comparing the inductance value with an inductance rated value, and if the difference value of the loss ratio and the loss ratio rated value is larger than a loss threshold value or the difference value of the inductance value and the inductance rated value is larger than an inductance threshold value, sending out an alarm by using an alarm device.
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