CN201945618U

CN201945618U - Current detector

Info

Publication number: CN201945618U
Application number: CN2010206185371U
Authority: CN
Inventors: 张伊辉; 李亚军
Original assignee: Cama Luoyang Electronics Co Ltd
Current assignee: Cama Luoyang Electronics Co Ltd
Priority date: 2010-11-16
Filing date: 2010-11-16
Publication date: 2011-08-24
Anticipated expiration: 2020-11-16

Abstract

The utility model discloses a current detector, which consists of a signal transmitter (ST), an impedance matching circuit, an oscillating circuit, a signal processing circuit and a microprocessor (MCU). A secondary coil of the ST is in series connection with a current transformer (CT) secondary circuit, a primary coil of the ST is connected to the high-frequency oscillation circuit, and the oscillation circuit realizes isolation of strong signals and weak signals through the ST. Impedance changes of the CT secondary circuit are reflected to the signal processing circuit, and acts of electric stealing which happen in a CT measurement circuit can be detected fast and accurately. Further specific manners of electric stealing can be recognized, and the four different manners of electric sealing such as a CT primary/ secondary short circuit and a CT primary/ secondary open circuit can be accurately distinguished.

Description

Current detector

(1) technical field

The utility model relates to the anti-electricity-theft application of electric energy measuring equipment.Mainly refer to current detector.

(2) background technology

Electric energy measuring equipment is as the foundation of power department to power consumption statistics and charge, and its accuracy and reliability are very important.But because the shortcoming and defect of existing anti-electricity-theft device and electric power meter itself provides opportunity for the electricity filching behavior of some power consumers.The electric energy of metering depends on the product of voltage, electric current, power factor three and time, changes above arbitrary key element, all can reach the purpose of stealing.Electricity filching means is of a great variety, concludes and gets up to mainly contain voltage method stealing, current method stealing, the stealing of misphase method, the stealing of expansion difference method.For voltage method stealing, the stealing of misphase method and the stealing of expansion difference method, all have the precautionary technology and the device of comparative maturity at present.And the current method stealing is a difficult point of anti-theft electricity technology always, for the electric energy measuring equipment that current return inserts through CT, some users by disconnect or short circuit CT once/the secondary side circuit, reach the purpose of stealing.Wherein especially with the most difficult strick precaution of fraudulent use electricity by short-circuit (stealing of U type), this stealing martingale is simple, and hidden-type is stronger, is easy to fast quick-recovery.At present, mainly rely on current method to detect,, then electricity filching behavior may take place if current anomaly reduces.This detection method accuracy rate is low, because the factor that causes electric current to reduce is a lot, therefore the situation of judging by accident, failing to judge happens occasionally, and has caused many negative effects for the work of power monitoring department.

(3) summary of the invention

The purpose of this utility model is exactly to propose a kind ofly to detect the electricity filching behavior that sets out at the CT measurement loop quickly and accurately.And can discern concrete stealing mode, accurately distinguish CT once/secondary short circuit, CT once/four kinds of different electricity filching means such as second open circuit.

For achieving the above object, technical scheme is made up of signal transmitting device (ST), impedance matching circuit, oscillatory circuit, signal processing circuit, microprocessor (MCU).Signal transmitting device secondary coil is serially connected in the CT secondary circuit, the elementary high-frequency oscillating circuits that connects.Oscillatory circuit is made up of low-power device, realizes the isolation of strong and weak signals by ST; The impedance variation of CT secondary circuit is reflected to signal processing circuit.

The utlity model has the effect of two aspects.1) by coupling and ST primary coil and CT secondary coil composition RLC parallel circuit, and satisfies certain condition of resonance, in order to amplify the impedance variation of CT secondary circuit.2) for different CT, the inductance L ct of secondary coil has some differences, and this judgement to CT secondary side state does not have any influence; But when carrying out the judgement of CT primary side state, can make the detected signal of MCU produce certain drift.At this situation, the influence that can come the erasure signal drift to cause by the device parameters of adjusting match circuit.

The high-frequency oscillation signal that oscillatory circuit produces is after the ST decay, the entering signal treatment circuit carries out filtering, amplify and amplitude transformation, it is transformed to the amplitude transformation that suitable MCU carries out the A/D sampling, export to MCU then, MCU regularly injects A by commutation circuit control detectable signal, B, C three-phase current loop, and the high-frequency signal that signal processing circuit is exported is carried out A/D sample, and calculate its all square amplitude, judge in view of the above CT once/the current physical state of secondary circuit, accurately distinguish CT once/the secondary short circuit, CT once/four kinds of different modes of connection such as second open circuit.

(4) description of drawings

Fig. 1 is the structural drawing of the utility model embodiment;

Fig. 2 is the schematic diagram of the utility model match circuit;

(5) embodiment

Be further described below in conjunction with the characteristics and the beneficial effect of drawings and Examples this utility model:

Fig. 1 is the structural drawing of the utility model embodiment, comprises signal transmitting device (ST), impedance matching circuit, oscillatory circuit, signal processing circuit, microprocessor (MCU).Alternating current sampling circuit, MCU are the existing functional parts of metering outfit, and the MCU and the alternating current sampling circuit of burglar-proof electric circuit are shared.ST is a special coupling transformer, and no-load voltage ratio K ≈ 1 secondary coil is serially connected in the CT secondary circuit, the elementary high-frequency oscillating circuits that connects.For power frequency component, the impedance of ST secondary coil is very little, and the caused pressure drop of the power current of flowing through is very little, and is also very little at the voltage signal of primary coil induction, thereby played the effect that strong and weak signals is isolated.For the high frequency detectable signal from the elementary injection of ST, impedance situation more complicated will be analyzed according to CT secondary side different wiring situation and combined impedance match circuit.

Claims

1. current detector, form by signal transmitting device (ST), impedance matching circuit, oscillatory circuit, signal processing circuit, microprocessor (MCU), signal transmitting device secondary coil is serially connected in the CT secondary circuit, the elementary high-frequency oscillating circuits that connects, oscillatory circuit are realized the isolation of strong and weak signals by ST; The impedance variation of CT secondary circuit is reflected to signal processing circuit.