F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention : METHOD OF DETECTING MALFUNCTIONING OF BREAKER USING NUMERICAL RELAY

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED

(b) NATIONALITY : An Indian Company.

(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001, State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to a circuit protection method and more particularly to a method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions.

BACKGROUND AND THE PRIOR ART

In a power system, protection relay plays an important role for proper and uninterrupted functioning of the healthy section of the system. The main objective of the protection relay is detection and tripping/blocking of the breaker, depending upon the application, in order to isolate the faulty section of the system from the healthy part.

Circuit breakers have one fixed contact and moving contact. During opening or tripping of breaker, the contacts get parted. If there is a wear and tear of the contacts, there is a possibility of high energy to get dissipated and heat to be generated. The breaker mechanical life depends on the number of breaker operations along with the amount of fault current passing through the contacts.

Some of the prior arts in the field of invention are as follows:

JP2001136653 (A) provides a neutral line open-phase protective breaker for a single- phase 3-wire system which is free from malfunctioning caused by high frequency noise. A common line is provided for overvoltage detection circuits which are provided between both voltage lines L1 and L2 and a neutral line N in order to detect the neutral line open-phase. A trip coil which trips a main circuit is connected in series to the overvoltage detection circuits in the common line.

JP2000032648 (A) provides for quick detection of the circuit breaker malfunctioning without delay, even if the circuit breaker is located on a non-power-supply end and the reception of the failure detection conditions of a failure close to the opposite end is delayed. This circuit breaker malfunctioning is detected, if a failure state lasts for a certain period of time under failure detection conditions OC1, OC2 and OC3 and circuit breaker tripping conditions 6a, 6b and 6c of a self-end line protector, which protects a power system as starting conditions and other circuit breakers connected to the same bus-bar of the self-end are released to remove the failure. Failure detection conditions OC4, OC5 and OC6, which transmitted from an opposite end, are received by the line protector and the circuit beaker malfunctioning is detected with the failure detection conditions from the opposite end and the circuit breaker tripping conditions 6a, 6b, and 6c of the self-end as staring conditions.

US2010326959 (A1) provides a gas insulated switchgear having, in a container where an arc-extinguishing gas is sealed, an arc-extinguishing chamber having a pair of arc contacts capable of contacting with/separating from each other, a puffer chamber formed by a puffer piston and a puffer cylinder provided on the side of one of the arc contacts, and a nozzle integrally fixed with said puffer cylinder, such that compression of said puffer chamber causes said arc-extinguishing gas to be led to said nozzle and blown onto an arc formed between said pair of arc contacts, whereby the arc is extinguished; wherein a part making up said arc contact, said puffer chamber or said arc-extinguishing chamber includes, as a marking substance, a substance including an element different from an element originally used for securing resistance or insulation resistance in the part, and said marking substance is released in gaseous form into said gas as said part wears down through thermal decomposition by heat from said arc.

JP2003281975 (A) provides wear detection equipment for a circuit breaker which can precisely detect a wear amount of an interrupting terminal by an operation of the circuit breaker with a simple structure. In the circuit breaker built in a gas insulating electric equipment, the circuit breaker is equipped with an interrupting operation detector to detect the operation of a circuit breaker and an interrupting current detector to detect an interrupting current value of the circuit breaker. When the circuit breaker detected by the interrupting operation detector is in operation, the interrupting current value detected by the interrupting current detector is processed to calculate wear amount of the interrupting terminal. The wear amount of this circuit breaker for every interrupting operation is cumulatively processed and an interrupting current monitoring device is provided to obtain cumulative wear amount.

JP2002083532 (A) provides for accurately detecting the amount of temperature variation by increase in contact resistance caused by the wear of a contact in a contact part without containing the amount of temperature variation in the contact part, a terminal part, or the like caused by current flowing in a circuit breaker, or temperature rising caused by loosening of a fastening crew for fastening an outer connecting wire to a fixed terminal. This circuit breaker is equipped with: a current processing means 100 outputting a trip signal based on current flowing in an electric circuit 10; a trip device 17 operating with the trip signal of the current processing means 100; a switch 18 switching the electric circuit 10 with the trip device 17; and a temperature detecting means 300 detecting temperature of a to-be- monitored part 31 whose temperature is monitored, and the detected result of the temperature detecting means 300 is corrected on the basis of current flowing in the electric circuit 10.

Although the given prior arts help in detecting circuit breaker malfunctioning, the method used is complex and may not always be effective. The present invention therefore provides a simple algorithm based method using logic units. The flex logic operand bit of the Output block (Breaker Arcing PKUP, OP and DPO becomes high or low depending upon the output of the algorithm flow logic)

OBJECTS OF THE INVENTION

A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to provide a method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions.

Other object of the present invention is to detect malfunctioning with respect to wear and tear of breaker contacts.

Other object of the present invention is to detect abnormal breaker arcing.
Yet another object of the present invention is to provide a simple and effective method of detecting malfunctioning of circuit breaker.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

There is provided a circuit protection method.

According to one embodiment of the present invention, there is provided a method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions by determining status of breaker arcing; determining status of breaker tripping; retrieving phase current value of each phase, calculating root mean square for each phase current for two cycles using an integrator; comparing said root mean square current to pickup value; providing output signal to a user defined hardware for corrective action.
Other embodiment of the present invention provides for capturing current analog samples per cycle and converting into digitized form using an analog/digital converter; said digitized samples from said analog/digital converter fed to a data acquisition and metering section; output from said data acquisition and metering section further fed to a CPU controller where the protection algorithm logic is processed; said CPU controller further generating the flex logic operand to said user defined hardware.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig 1 illustrates the method of circuit protection by detecting malfunctioning using different elements present in numerical relay in accordance with the present invention.

Fig. 2 illustrates the protection algorithmic logic being processed in CPU controllers.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Reference is first invited to Fig 1 where the supervision of breaker contacts using a numerical relay under a predefined set of conditions. It shows different units like Data acquisition and metering section, CPU controller, Numerical relay etc.

Fig. 2 shows the processing of logic in the numerical relay. It provides different method steps used in detecting malfunctioning of a breaker.

Fig. 3 illustrates current and voltage samples of the breaker arcing condition.

The invention therefore provides a method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly in the present invention a method of supervising the breaker contacts in order to check the healthiness of breaker is provided. This function is related to detection of malfunctioning of breaker in respect of wear and tear of breaker contacts and breaker arcing phenomena. Breaker arcing is very critical as it can result to massive explosion of the breaker and eventually hazardous explosion in the switchboard. This logic will be used in a numerical relay as a part of LV/MV switchboards. The algorithm will go as flow logic into the firmware build or embedded systems of the relay.

This document elucidates the application space and concept of Breaker arcing algorithm and illustrates the HMI settings and the firmware logic to be incorporated to include this feature in New Feeder Protection relay.

Fig. 1 depicts the flow of the inputs /commands to the corresponding hardware of the numerical relay. There are numerous components in terms of embedded systems (hardware) in the numerical relay of which Data acquisition & metering and CPU controller are the two main sub sections of the relay. Initially the current transformer secondary inputs i.e. phase currents which are analog inputs are fed to the Analog/Digital (A/D) converter located inside the relay. The A/D converter captures the current analog samples per cycle and converts into digitized form. 64 samples / cycle are captured by the A/D converter. These digitized samples from A/D converter go into the Data acquisition and metering section of the numerical relay and further to the protection algorithm logic. The protection algorithm logic is installed in the CPU controller, in a coded form, which is embedded inside the relay. Through Data acquisition and metering section, the current inputs advance to CPU controller where the protection algorithm logic is processed.

Here in this case after the procession of the logic, the Boolean logic operand gets high when breaker arcing feature picks up and it is mapped to digital output of the relay. The digital output gives the command to the user defined hardware, if needed.

Circuit breakers have one fixed contact and moving contact. During opening or tripping of the breaker, the contacts get parted. If there is a wear and tear of the contacts, there is a possibility of high energy to get dissipated and heat to be generated. Though we will be having preventative maintenance for breaker mechanical life but still this feature will aid in estimating the contacts healthy condition. The breaker mechanical life depends on the number of breaker operations along with the amount of fault current passing through the contacts. The second aspect has been considered here in this feature.

Settings:-
The following settings are required on the HMI:-
Breaker Arcing blocking:- Enabled/Disabled
Breaker Arcing pickup settings:- 10 to 60000 (KA)^2 for a period of 2 cycles
Separate Flex logic element has to be added in Flex logic screen (Breaker Arcing PKUP,
Breaker Arcing OP, Breaker Arcing DPO)

Inputs:-
Status of the breaker arcing feature (enabled/disabled)Three Phase currents (Ia, Ib, Ic)
Breaker Trip status (open/close)

Output:-

The flex logic operand bit of the Output block (Breaker Arcing PKUP, OP and DPO becomes high or low depending upon the output of the algorithm flow logic)

Abbreviations used:

CPU: Central processing unit
A/D: Analog to digital
PKUP: pickup
OP: operate
DPO: drop out
DI: digital input

Validation data and results
Using the Matlab Sim Power Systems tool, circuit was developed to achieve breaker arcing conditions for simulation. The current and voltage samples of the breaker arcing condition as shown in figure 3 are obtained from the Matlab scope for validation of algorithm logic.

The current samples of the waveform obtained as illustrated in figure 3 were fed into the firmware for testing and it is found that the algorithm logic is working fine.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM

1. A method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions, said method comprising the steps of: determining status of breaker arcing (Enable/Disable); determining status of breaker tripping; retrieving phase current value of each phase, determining root mean square for each phase current for two cycles using an integrator; comparing said root mean square current to pickup value; providing output signal to a user defined hardware for corrective action.

2. Method as claimed in claim 1 comprising the steps of capturing current analog samples per cycle and converting into digitized form using an analog/digital converter; said digitized samples from said analog/digital converter fed to a data acquisition and metering section; output from said data acquisition and metering section further fed to a CPU controller where the protection algorithm logic is processed; said CPU controller further generating the flex logic operand to said user defined hardware.

3. Method as claimed in claim 1 further comprising a step wherein values for breaker arcing pickup, breaker arcing output and breaker arcing dropout fed to a flex logic screen to determine said malfunctioning.

4. Method as claimed in claim 1 used for detecting said malfunctioning with respect to wear and tear of breaker contacts.

5. Method as claimed in claim 1 used for detecting abnormal breaker arcing.

6. A method of detecting malfunctioning of breaker by supervising breaker contacts using a numerical relay under a predefined set of conditions as herein described and illustrated with respect to the accompanying drawings.