WO2015080569A1

WO2015080569A1 - An automatic power fault detection method and system for monitoring and controlling a power distribution system

Info

Publication number: WO2015080569A1
Application number: PCT/MY2014/050011
Authority: WO
Inventors: Lee Soon Tan
Original assignee: Lee Soon Tan
Priority date: 2013-11-28
Filing date: 2014-11-27
Publication date: 2015-06-04
Also published as: WO2015080569A4

Abstract

The present invention relates to a method for monitoring and controlling a power system, characterised by the steps of: identifying a fault exceeding a predetermined threshold current in the power distribution system; verifying the identified fault to confirm the fault; generating a digital signal upon fault confirmation; wherein the digital signal activates protective operations against the fault, comprising the steps of: isolating a power supply to an electrical load; and counting a number of fault occurrence; wherein the power supply to the electrical load is restored if the number of fault occurrence is within a predetermined setting; and the power supply to the electrical load remains isolated if the number of fault occurrence exceeds the predetermined setting. An automatic power fault detection system is also disclosed in the present invention.

Description

AN AUTOMATIC POWER FAULT DETECTION METHOD AND SYSTEM FOR MONITORING AND CONTROLLING A POWER DISTRIBUTION SYSTEM

Background of the Invention Field of the Invention

This invention relates to an automatic power fault detection method and system for monitoring and controlling a power distribution system, and more particularly to a method for protecting against power fault disturbances. Description of Related Arts

In an electrical power system, a fault is an abnormal flow of current. Short circuit is one of the most common power faults. It occurs when an incoming current travels from "live" to "neutral" and bypasses a normal load. Fault may also be caused by overcurrent, which is an abnormal current flow higher than the normal value of current flow in a load of an electrical circuit. In the occurrence of an earth fault, the leakage is flowing from circuit to ground. Other general power faults include surges, nuisance, harmonic, lightning, and power surge.

To date, a number of protective devices have been addressed to detect fault conditions to limit the loss of service due to a failure. For example, miniature circuit breaker (MCB) (Bayliss, C, 2012) is introduced to provide protection against overloads and short circuits, which can cause damage to cables and equipment. Earth leakage circuit breaker (ELCB) or residual current circuit breaker (RCCB) is intended to detect currents leaking to earth from an installation and disconnect the power in order to prevent electric shock. It allows protection against earth fault ranging from 10 imA to 300 imA, and in some instances, exceeding 300 imA. However, ELCB or RCCB trips frequently when power surges/harmonic/transient/nuisance/lightning strike arise, which cause to unwanted disruption of equipment operation. Thus, technical personnel have to standby and attend to the site for restoration whenever necessary. The conventional protective devices are able to detect current as low as 10 mA. However, the protection sensitivity is meant to protect equipment but not the user. According to an Underwriters Laboratories (UL) report (IEEE On-line Communities), a current through the body greater than 5 mA is considered unsafe. This current level can cause to a startle reaction that will result in a serious injury. While 5 mA is the upper limit for safety in the general population, a current of above 2.5 mA has made it difficult for most people to release grip from the electric shock. On the other hand, a low tripping threshold value has the drawback as well in the respect that it will cause to frequent nuisance tripping.

The power protective method of the present invention is designed to overcome most of the faults by detecting leakage current at a minimum of 2.5 mA, which complies with IEC 60479 safety requirements. Preferably, the method detects and identifies a current of 2.5 mA, 5 mA, 10 mA, 15 mA, 30 mA, 50 mA, and 1 00 mA.

In the prior art, when a power fault is detected, a mechanical mechanism will be triggered to disconnect the power supply. In the present invention, a method operated based on electronic circuit is adapted to detect and process the fault. Subsequent to the process, the fault is analysed to determine an electricity performance before jumping into tripping, and thus, unnecessary power disturbance can be avoided.

Furthermore, additional features which including optional tripping threshold, earth leakage current detection, remote control and monitoring of the power distribution system are incorporated to the current system. The versatile features of the system are designed according to the Energy Commission Electricity of Malaysia Regulations 1994 of 35, 36(1 ), 36(2), 36(3), 36(4) and all the amendments as stipulated. WO Patent Publication number 2010100428 discloses a method and an apparatus for detecting power supply fault in a Multiple Earth Neutral power distribution system. The apparatus comprises a detector to determine electrical status of earth line; a processor to determine an associated fault, wherein the processor may be set to a certain threshold to determine a fault condition ; an electricity meter to carry out metering function and fault determination; a current detector to detect the current in the active line; a meter for displaying meter information or fault condition ; and a relay control to enable switching of power supply. The electricity meter may further provide an intelligent function for remote operation. The apparatus detect fault in power supply by determining a differential current between the active and neutral conductors to determine an earth current value. Subsequently, a fault associated with the determined earth current value is identified. The embodiments of this invention enable direct measurement of a differential current in order to determine a fault. Nevertheless, current threshold for fault determination is not defined in this prior art, and thus the protection level provided by the system might be limited. Additional features such as fault diagnostic analysis, compliance to a range of power distribution system standards, generation of digital signal for the integration of centralised management-control system (CMS) are also absent in the prior art.

Accordingly, it can be seen in the prior arts that there exists a need to provide an automatic power fault detection method for monitoring and controlling a power system to achieve a power system with reliable performance. This statement is to make clear to the examiner what is the problem in the prior art being solved by the present invention. References

• Bayliss, C, Transmission and Distribution Electrical Engineering, 2012 Summary of Invention

It is an objective of the present invention to provide an automatic power fault detection method to achieve a stable power distribution system by minimising unintentional power disruptions. It is also an objective of the present invention to provide an electronic circuitry-operated method for current protection against fault conditions including lightning, earth fault, short circuit, power surges, transient, and harmonic interruption.

It is yet another objective of the present invention to provide an automatic fault detection system with high level of personal protection from shock hazards by providing current detection sensitivity at a minimum of 2.5 imA. Accordingly, these objectives may be achieved by following the teachings of the present invention. The present invention relates to an automatic power fault detection method for monitoring and controlling a power distribution system, characterised by the steps of: identifying a fault exceeding a predetermined threshold current in the power distribution system; verifying the identified fault to confirm the fault; generating a digital signal upon fault confirmation; wherein the digital signal activates protective operations against the fault, comprising the steps of: isolating a power supply to an electrical load; and counting a number of fault occurrence; wherein the power supply to the electrical load is restored if the number of fault occurrence is within a predetermined setting; and the power supply to the electrical load remains isolated if the number of fault occurrence exceeds the predetermined setting. An automatic power fault detection system is also disclosed in the present invention.

Brief Description of the Drawings

The features of the invention will be more readily understood and appreciated from the following detailed description when read in conjunction with the accompanying drawings of the preferred embodiment of the present invention, in which:

Fig. 1 is a block diagram showing an automatic power fault detection system for monitoring and controlling a power distribution system with one control application. Fig. 2 is a block diagram showing an automatic power fault detection system for monitoring and controlling a power distribution system with two controls application. Fig. 3 is a block diagram showing an automatic power fault detection system for monitoring and controlling a power distribution system with two controls application incorporated with centralised management-control system (CMS) operation. Fig. 4 is a circuitry diagram of a distribution board illustrating a preferred embodiment of the present invention for use in an instant water heater application.

Fig. 5 is a circuitry diagram of a distribution board illustrating a single-phase system with one control application provided with an automatic power detection system of the present invention.

Fig. 6 is a circuitry diagram of a distribution board illustrating a three-phase system with one control application provided with an automatic power detection system of the present invention.

Fig. 7 is a circuitry diagram of a distribution board illustrating a single-phase system with two controls application provided with an automatic power detection system of the present invention. Fig. 8 is a circuitry diagram of a distribution board illustrating a three-phase system with two controls application provided with an automatic power detection system of the present invention.

Fig. 9 is a circuitry diagram of a distribution board illustrating a single-phase system with two controls application provided with an automatic power detection system of the present invention incorporated with CMS operation. Fig. 10 is a circuitry diagram of a distribution board illustrating a three-phase system with two controls application provided with an automatic power detection system of the present invention incorporated with CMS operation. Detailed Description of the Invention

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for claims. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims. As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words "include," "including," and "includes" mean including, but not limited to. Further, the words "a" or "an" mean "at least one" and the word "plurality" means one or more, unless otherwise mentioned. Where the abbreviations or technical terms are used, these indicate the commonly accepted meanings as known in the technical field. For ease of reference, common reference numerals will be used throughout the figures when referring to the same or similar features common to the figures. The present invention will now be described with reference to Figs. 1 -10.

The present invention relates an automatic power fault detection method for monitoring and controlling a power distribution system, characterised by the steps of:

identifying a fault exceeding a predetermined threshold current in the power distribution system;

verifying the identified fault to confirm the fault;

generating a digital signal upon fault confirmation; wherein the digital signal activates protective operations against the fault, comprising the steps of:

isolating a power supply to an electrical load; and

counting the number of fault occurrence;

wherein the power supply to the electrical load is restored if the number of fault occurrence is within a predetermined setting; and

the power supply to the electrical load remains isolated if the number of fault occurrence exceeds the predetermined setting. In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the fault comprises lightning, earth fault, short circuit, power surges, transient, and harmonic.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the predetermined setting is optionally reset to restore the power supply to the electrical load if the number of fault occurrence exceeds the predetermined setting.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the predetermined threshold current has a minimum value of 2.5 imA.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the predetermined threshold current is selected from a value ranging from 2.5 imA to 300 imA.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the predetermined setting is an intermittent counting of fault occurrence and the threshold number of fault occurrence is selected from a group consisting of 1 , 2, 4, 7, 14, and 28. In another embodiment, no limit of number of fault occurrence is given to the predetermined setting. In a further embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the predetermined setting is a continuous counting of fault occurrence and the threshold number of fault occurrence is more than one.

In a further embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, when a power fault is detected and confirmed, the power supply to the electrical load is isolated in less than 36 ms.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the method further comprises detecting whether the power distribution system is earthed and isolating the power supply to the electrical load in the absence of the earthing.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the method further comprises detecting whether the power distribution system is connected to live and neutral and isolating the power supply to the electrical load in the absence of live or neutral or both.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the method can detect an overcurrent or short-circuit fault and isolating the power supply to the electrical load in the presence of the overcurrent or short-circuit fault.

In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the method can detect an overcurrent or short-circuit fault from 6 A to 300 A. In a preferred embodiment of the automatic power fault detection method for monitoring and controlling a power distribution system, the method can detect a short-circuit fault from 3 kA to 50 kA. The present invention also provides an automatic power fault detection system for monitoring and controlling a power distribution system according to the automatic power fault detection method, characterised by:

a fault detector (1 ) for detecting a fault in a power distribution system;

a fault processor (2), connected to the fault detector (1 ), for confirming the fault;

an actuator means (3), responsive to the confirmed fault, for generating a first digital signal;

an automatic reset controller (14) comprising a counter setting (12), for measuring a number of fault occurrence and a repeat fault down (13), for identifying a continuous fault occurrence;

a fault diagnostic controller (10) in communication with the counter setting (12) and repeat fault down (13) to generate a second digital signal; and an on/off controller (8), responsive to the first or second digital signal, for isolating or restoring a power supply to an electrical load (7).

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the fault detector (1 ) has a minimum detection sensitivity of 2.5 imA.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system further comprises a live/neutral indicator (4) or an earth indicator (5) or a combination thereof.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system further comprises a manual testing module (6) or a manual reset controller (1 1 ) or a combination thereof.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system is incorporated with an automatic testing means (9) for simulating a fault occurrence every 24 hours.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system is monitored and controlled by a centralised management-control system (CMS) (15).

Below is an example of an automatic power fault detection system for monitoring and controlling a power distribution system from which the advantages of the present invention may be more readily understood. It is to be understood that the following example is for illustrative purpose only and should not be construed to limit the present invention in any way. Examples

Figure 1 illustrates the flow of the automatic power fault detection system initiated by a power fault detection. Figure 2 demonstrates an exemplary embodiment of the automatic power fault detection system with two electrical loads, in which two detection systems are operated simultaneously to protect the electrical loads and user.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the power distribution system comprises live, neutral, and earth lines. The power system can be distributed through a one-phase electrical system or a three-phase electrical system. In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the fault detector (1 ) has a minimum detection sensitivity of 2.5 imA. In one embodiment, the fault detector (1 ) is a component to detect a fault such as residual current, short circuit, and surges, for example, the fault detector (1 ) may be a zero current transformer (ZCT). In the operation of a fault detector (1 ) having 2.5 imA detection sensitivity, an incoming fault with a residual current of 2.5 imA or greater will be detected by the fault detector (1 ) and passes through the fault processor (2). The fault processor (2) filters alternating current (AC) noise by using capacitor and allows a fault with confirmed current to activate the actuator means (3), and thus isolating the power supply upon the first digital signal generation.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the fault detector (1 ) may have a detection sensitivity of 2.5 imA, 5 imA, 10 imA, 15 imA, 30 imA, 50 imA, 100 imA or >100 imA. In a particular embodiment, the fault detector (1 ) is provided with at least two detection sensitivity settings selected from the group consisting of 2.5 mA, 5 mA, 10 imA, 15 imA, 30 imA, 50 imA, 100 imA and >100 imA, which allows the user to manually select a detection sensitivity appropriate to a specific electrical load (7).

It can be seen that an automatic power fault detection system with low leakage protection is desirable for an electrical load in a place where the floor is likely to be wet or the enclosure is of low electrical resistance. For instance, an automatic power fault detection system provided with a fault detector (1 ) having a detection sensitivity of 2.5 mA may be used for an instant water heater (Figure 4). In another embodiment where an electrical load is installed in a place of public entertainment, the fault detector (1 ) may have a detection sensitivity not exceeding 5 mA. The present invention can serve to provide protection for use of home theatre system, CCTV, personal computer, auto gate, and fish pond. In yet another embodiment where an electrical load is a hand-held equipment, apparatus, or appliance, the detection sensitivity of the fault detector (1 ) may not exceed 30 imA. Generally, a detection sensitivity less than 30 imA is suitable for overall home appliances.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the counter setting (12) counts a number of fault occurrence and a second digital signal will be generated to restore power supply or maintain the isolation of power supply based on a predetermined setting. However, when the fault occurs in a continuous manner, repeat fault down (13) will supersede the counter setting (12) by generating a second digital signal to maintain the isolation of power supply to the electrical load (7) without counting the number of fault.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the on/off controller (8) is a contactor, robotic arm, switching mechanism or switch gear.

In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system further comprises an earth indicator (5). In one embodiment, a light source is connected to the earth indicator (5) to indicate the presence or absence of the earthing. Preferably, the light source is a light emitting diode (LED) or a neon lamp. The colour of the light source is, not but limited to green colour. The LED or the neon lamp is activated in the presence of earthing. In a preferred embodiment of the automatic power fault detection system for monitoring and controlling a power distribution system, the automatic power fault detection system is monitored and controlled by a centralised management-control system (CMS) (15), as shown in Figure 3. The CMS can be operated through a network communication backbone such as Global System for Mobile Communications (GSM), LAN/WEB/lntranet/ETHERNET module with pre-programmed software operation. When a power fault is detected, the fault diagnostic controller (10) will generate a digital signal. The digital signal is converted to text message and sent to a user or a control centre though the network communication backbone. From the digital signal received, the user or the control centre can select appropriate action to perform in response to the power fault, for example, to reset the predetermined setting in order to restore the power supply to the electrical load.

Figures 5 - 10 illustrate circuitry diagram of distribution board designed for different application fields, such as home, working station, and industry with various power consumptions. A standard power distribution system for USA and related countries in a Low Voltage (LV) industry will be 1 10 VAC for single phase and 220 VAC for three phase; and 230 VAC for single phase and 415 VAC for three phase for UK, Malaysia and related countries. Figure 5 is a circuitry diagram of a distribution board illustrating a single-phase system with one control application provided with an automatic power detection system of the present invention. Figure 6 illustrates a circuitry diagram of a distribution board for a three-phase system with one control application, provided with an automatic power detection system of the present invention. Figure 7 is a circuitry diagram of a distribution board illustrating a single-phase system with two controls application provided with an automatic power detection system of the present invention. Figure 8 is a circuitry diagram of a distribution board illustrating a three-phase system with two controls application provided with an automatic power detection system of the present invention.

Figure 9 is a circuitry diagram of a distribution board illustrating a single-phase system with two controls application provided with an automatic power detection system of the present invention incorporated with CMS operation. Figure 10 is a circuitry diagram of a distribution board illustrating a three-phase system with two controls application provided with an automatic power detection system of the present invention incorporated with CMS operation. The distribution boards incorporated with CMS serve to manage and provide remote accessibility to power distribution system in remote area, work station with high transmission power, and sites which required immediate attention in case of system down. Although the present invention has been described with reference to specific embodiments, also shown in the appended figures, it will be apparent for those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined in the following claims.

Claims

I/We claim:

An automatic power fault detection method for monitoring and controlling a power distribution system, characterised by the steps of:

verifying the identified fault to confirm the fault;

generating a digital signal upon fault confirmation;

wherein the digital signal activates protective operations against the fault, comprising the steps of:

isolating a power supply to an electrical load; and

counting a number of fault occurrence;

the power supply to the electrical load remains isolated if the number of fault occurrence exceeds the predetermined setting.

An automatic power fault detection method for monitoring and controlling a power distribution system according to claim 1 , wherein the fault comprises lightning, earth fault, short circuit, power surges, transient, and harmonic.

An automatic power fault detection method for monitoring and controlling a power distribution system according to claim 1 , wherein the predetermined setting is reset to restore the power supply to the electrical load if the number of fault occurrence exceeds the predetermined setting.

An automatic power fault detection method for monitoring and controlling a power distribution system according to claim 1 , wherein the predetermined threshold current has a minimum value of 2.5 imA.

5. An automatic power fault detection method for monitoring and controlling a power distribution system according to claim 1 , wherein the method further comprises detecting whether the power distribution system is earthed and isolating the power supply to the electrical load in the absence of the earthing.

6. An automatic power fault detection method for monitoring and controlling a power distribution system according to claim 1 , wherein the method further comprises detecting whether the power distribution system is connected to live and neutral and isolating the power supply to the electrical load in the absence of live or neutral or both.

7. An automatic power fault detection system for monitoring and controlling a power distribution system according to the method of claim 1 , characterised by:

a fault detector (1 ) for detecting a fault in a power distribution system;

a fault diagnostic controller (10) in communication with the counter setting (12) and repeat fault down (13) to generate a second digital signal; and

an on/off controller (8), responsive to the first or second digital signal, for isolating or restoring a power supply to an electrical load (7).

8. An automatic power fault detection system for monitoring and controlling a power distribution system according to claim 7, wherein the fault detector (1 ) has a minimum detection sensitivity of 2.5 imA.

9. An automatic power fault detection system for monitoring and controlling a power distribution system according to claim 7, wherein the automatic power fault detection system further comprises a live/neutral indicator (4) or an earth indicator (5) or a combination thereof.

10. An automatic power fault detection system for monitoring and controlling a power distribution system according to claim 7, wherein the automatic power fault detection system further comprises a manual testing module (6) or a manual reset controller (1 1 ) or a combination thereof.

1 1 . An automatic power fault detection system for monitoring and controlling a power distribution system according to claim 7, wherein the automatic power fault detection system is incorporated with an automatic testing means (9) for simulating a fault occurrence every 24 hours.

12. An automatic power fault detection system for monitoring and controlling a power distribution system according to claim 7, wherein the automatic power fault detection system is monitored and controlled by a centralised management-control system (CMS) (15).