WO2022055456A1

WO2022055456A1 - Residual current tracking method and apparatus in low voltage power distribution systems

Info

Publication number: WO2022055456A1
Application number: PCT/TR2021/050896
Authority: WO
Inventors: Celal KORAŞLI
Original assignee: Hasan Kalyoncu Üni̇versi̇tesi̇
Priority date: 2020-09-08
Filing date: 2021-09-07
Publication date: 2022-03-17
Also published as: EP4097496A1; EP4097496A4; TR202014177A2

Abstract

The invention is about a residual current tracking method and apparatus in low voltage power distribution systems; that has a microcontroller based control circuit to track residual currents in all protective earthing (PE) conductors of power distribution systems used for neighborhoods, commercial, medical services and similar places, perform early detection of residual currents caused by electrically, mechanically or chemically decomposed insulations without posing any hazard for the user and gain the advantage of determining the faulty feeder and the defects for it continuously monitors the residual current passing through all PE conductors and provides operating data of all feeders, and its' characteristic is being consisted of the following operation steps; detection of residual current (100) by means of each protective earthing conductor (6) sequentially passing through hall effect current sensors (7), filtering of residual current (200) by the RC active low pass band filter (8) for external electrical statics, using the amplifier (9) amplifying the analogue voltage signal (300) corresponding to the residual current, averaging the analogue voltage signal (400) corresponding to the residual current with the integrator (10), converting the averaged signals to numerical form (500) with the analogue/digital convertor, making the diagnostic tests (600) of the signals received within a specified time over the microcontroller (11), with the data displayed on the display (13) informing (700) the user with the wireless signal transmitter (14) about a danger when signals exceed the preset values, initiating a new process order (800) following information and after the time specified by the user, the microcontroller (11) stopping the process (900) in a case of danger such as detection of a short circuit fault passing through any one of the protective earthing conductors (6), the display (13) displaying the number of the faulty feeder (100) and warning the user (1100) for the short circuit fault.

Description

RESIDUAL CURRENT TRACKING METHOD AND APPARATUS IN LOW

VOLTAGE POWER DISTRIBUTION SYSTEMS

Technological Area:

The invention is about a residual current tracking method and apparatus in low voltage power distribution systems; that has a microcontroller based control circuit to track residual currents in all protective earthing (PE) conductors of power distribution systems used for neighborhoods, commercial, medical services and similar places, perform early detection of residual currents caused by electrically, mechanically or chemically decomposed insulations without posing any hazard for the user and gain the advantage of determining the faulty feeder and the defects for it continuously monitors the residual current passing through PE conductors and provides operating data of all feeders.

Current Situation of the Technique:

Residual current circuit breakers (RCCB) are important devices that provide safety not only for humans but also for animals in housings, commercial and industrial establishments. They're installed in all distribution boards providing lighting and power load. Their working principle is about the current difference between phase and neutral conductors which provide load, known as the residual current. In well protected systems, the system flows from PE conductor to earthing conductor. Main sources of residual current are the dielectricity of system cables, the filter capacitors protecting electrical devices, the capacitances of longer cables, the damages or defects on the dielectric materials of semi-conductors and condensers, the defects in the component materials or improper earthing in the equipment. The presence of this current may lead to big results; it may cause dangerous voltage raises in accessible conductive parts of the working equipment. There may be even worse situations in medical applications for the risks it may pose both for the patients and for the health workers. That's why it must be kept under the acceptable safe limit.

According to an international standard inscripted as IEC-60960-1, the magnitude of residual current should always be less than 3.5mA for constant equipment used in house and offices except the hand-use mobile equipment limited with 0.25mA. For medical devices this limit is 0.5mA and under different working conditions 1mA before reaching critical limits. These limits enable the current for these equipment to be limited with a level in order to prevent people get harmed while touching or getting in contact with the open metal parts of these equipment.

In present applications, residual current is measured separately for each feeder, with plier type tools covering phase and neutral conductors. For the measurements are made at intervals, it may be late to take required correction measures and thus it makes this method both time consuming and costy.

In the patent application numbered US8605394B2, the "Device, method and system to track residual current and detect failures in electric systems" is described. In this patent study, a method is offered and an apparatus is suggested to track residual current. The current detection in this application; is made with the power feeding line and a single toroidal current transformer wrapped around a neutral conductor.

Both two methods mentioned above which are used to track residual current, are lack of detecting the faulty feeder in an instant. Besides it takes time and effort to conduct the tests. For the system sensitivity is low, the results are not likely to be more reliable. And for upper current limits are not high, it cannot be applied on distribution systems with lots of columns and lines in design.

In conclusion, there's a need for an easy-to-use, low-cost, time-saving new technology that can overcome the disadvantages mentioned above, processes residual current data, compares them with safe limit values, displays current values and informs the nearest user in cases of danger. Definition of Invention:

This invention is a residual current tracking method and apparatus in low voltage power distribution systems and its' characteristic is being an easy-to-use, low-cost, time-saving new technology that can overcome the disadvantages mentioned above, processes residual current data, compares them with safe limit values, displays current values and informs the nearest user in cases of danger.

In order to fulfil all purposes mentioned above and revealed by the detailed description below the invention describes; a system that continuously tracks the residual current passing through all PE conductors to check safety breaches, gives early warning signals by measuring residual current within each PE conductor and is able to instantly detect and identify the faulty feeder.

The system subject to invention describes a method for measuring and tracking the residual current passing through all of the PE conductors of a power distribution system. Residual current circuit breakers (RCCB) are considered as the last protection equipment for safety breaches. Current detection and measurement modules monitored by microcontroller are easy and low-cost technologies. In the system subject to invention, microcontroller processes the residual current data and compares it with the safe limit set forth in an international standard inscripted as IEC-60960-1. In a case of breach, invention displays these values and informs the nearest user. In addition, in case of an RCCB cut in an undesired feeder failure, microcontroller stops the process and determines the faulty feeder. Microcontroller uses a customizable software to continuously monitor the events in a specific order, in order to take required measures and maintain the sustainability of the power supply.

All the advantages of the method subject to system will be understood more clearly with the scheme given below and the detailed description written referring this scheme, for this reason, the assessment should be made considering this scheme and the detailed description. Description of Figures:

Invention will be explained by referring to the annexed figures this way function and characteristics of the invention will be understood more clearly but this is not intended to limit the invention with these specific arrangements. Contrary, it's intended to cover all alternatives, changes and equivalencies that can be included in the area the invention is described in by the claims in the annex. It's best to note that shown details are demonstrated and presented only for the purpose of explaining the preferred arrangements of the current invention and providing the most practical and easy definition of both the development of methods and the rules and conceptual features of the invention. In these figures;

Figure 1. Circuit scheme view of the system subject to invention.

Figure 2. Schematic view of the operation mechanism of the system subject to invention.

Figures that will help to understand this invention are numbered as specified in the annexed picture and they are given below by their names.

Description of References:

1. RCCB Unit

2. First Phase and Neutral Cables

3. Second Phase and Neutral Cables

4. Earthing Conductor

5. Earthing Terminal

6. Protective Earthing Conductor

7. Current Sensor

8. Filter

9. Amplifier

10. Integrator

11. Microcontroller 12. Display Driver

13. Display

14. Signal Transmitter

15. Connector

16. Current detection module

17. Processing Module

100. Detection of Residual Current

200. Filtering of Residual Current

300. Amplifying the Analogue Voltage Signal

400. Averaging the Voltage Signal

500. Converting to Numerical Form

600. Conducting Diagnostic Tests

700. Informing

800. Initiating a New Process Order

900. Stopping the Process

1000. Displaying the Number of the Faulty Feeder

1100. Warning the User

Description of Invention:

The invention is composed of; a current detection module (16) and a processing module (17) embedded into the modular RCCB unit (1).

The current detection module (16) subject to invention has; at least one hall effect current sensor (7) where at least one protective earthing conductor (6) passes through and that detects residual current, a filter (8) that eliminates induced static from the close by conductives or electronic circuits or possible over-current signal peaks, at least one amplifier (9) that amplifies the conditioned voltage signals and an integrator (10) that averages the current signal before being sent to the processing module (17).

The processing module (17) subject to invention has; at least one microcontroller (11) that analyses, stores the data and compares them with the preset values, at least one analogue/digital multiplexer connected to the analogue input of the microcontroller (11), a display (13) and a wireless signal transmitter (14) that informs the user on the presets and any case of danger.

The processing module (17) subject to invention includes a wireless signal transmitter (14) that informs the user in any case of danger with data transferring features such as bluetooth, WiFi or RFID.

The invention consists of the following operation steps; detection of residual current (100) by means of each protective earthing conductor (6) sequentially passing through hall effect current sensors (7), filtering of residual current (200) by the RC active low pass band filter (8) for external electrical statics, using the amplifier (9) amplifying the analogue voltage signal (300) corresponding to the residual current, averaging the analogue voltage signal (400) corresponding to the residual current with the integrator (10), converting the averaged signals to numerical form (500) with the analogue/digital convertor, making the diagnostic tests (600) of the signals received within a specified time over the microcontroller (11), with the data displayed on the display (13) informing (700) the user with the wireless signal transmitter (14) about a danger when signals exceed the preset values, initiating a new process order (800) following information and after the time specified by the user, the microcontroller (11) stopping the process (900) in a case of danger such as detection of a short circuit fault passing through any one of the protective earthing conductors (6), the display (13) displaying the number of the faulty feeder (100) and warning the user (1100) for the short circuit fault.

Detailed Description of Invention:

Basic components included in the system subject to invention are; the modular RCCB unit (1), the first phase and neutral cables (2), the second phase and neutral cables (3), the earthing conductor (4), the earthing terminal (5), the protective earthing conductor (6), the current sensor (7), the filter (8), the amplifier (9), the integrator (10), the microcontroller (11), the display driver (12), the display (13), the wireless signal transmitter (14), the connector (15), the current detection module (16) and the processing module (17).

The invention describes a control circuit including a hall effect current sensor (7) for the detection of residual current (100) passing through protective earthing conductors (6). Filtering of the residual current (200) from each current sensor (7), is made by the low pass RC filter (8). Then, prior to processing of signals by the microcontroller (11), amplifying the analogue voltage signals (300) corresponding to the current values, is made by the amplifier (9). All non-standard current magnitudes are displayed on a 3- digits 7-segments display (13) operated by the related display driver (12) and transmitted to the user by a wireless signal transmitter (14).

The algorithm of the invention, referring to the Figure 2; is based on the current sensors (7) detecting the residual current (100) sequentially passing through the earthing conductors (6) starting from the first one. The current signal caused by magnetic inductions from possible external electrical statics, is filtered by an RC active low pass filter (8). The analogue voltage signal corresponding to the residual current signal, is amplified (300) by the amplifier (9). Then, prior to converting of the signals to numerical form (500) by the analogue-digital convertor embedded to microcontroller (11), the analogue voltage signal is averaged (400) by the integrator (10) to eliminate the peaks and average them over the feeding system period. Diagnostic tests on obtained data (600) are made by the microcontroller (11). In case of detecting a residual current magnitude bigger than the limit values preset by the user, the microcontroller (11) sends warning signal to the user for information purpose and at the same time displays the numbers of the protective earthing conductors (6) and the data on current magnitude on the display (13). After a specified time passes, a new process order is initialized (800) for the next measurement phase. In extraordinary situations, for instance in case of detecting a short circuit fault passing through one of the protective earthing conductors (6), the microcontroller (11) stops the process (900) and again displays the number of the faulty feeder (1000) and warns the user (1100) after displaying the current value as zero. Referring to the block diagram of the invention shown in Figure 1, both the current detection module (16) and the processing module (17), are designed in a way to be embedded into the molded casing of the PC board of the residual current circuit breaker (RCCB). Functions of these two modules are as follows:

1 . In the presented application a 4-pole modular RCCB unit (1) is used. The four phase (LI, L2, L3) and the neutral phase (NT) cables are connected to the feeder lines through the first phase and neutral cables (2) and the second phase and neutral cables (3) of the RCCB unit to meet the loads. The left-open metal parts of the loads are connected to the earthing terminal (5) with protective earthing conductors (6). The earthing line is directly connected to the earthing conductor (4) of the distribution system. The invention is developed in a way to comply with all PC boards and to allow all 4-pole RCCB types in the market to be integrated to the current detection module (16) and the processing module (17) of the invention.

In the invention, the residual current passing through each protective earthing conductor (6), is detected by the hall effect current sensor (7) known for its' precise, reliable and isolated detection even at high passing current levels. There are eight current sensors (7) used in the application which's offered with standard 8-bit based integrated circuits (IC) to facilitate the process. These are connected to the current detection module (16) with socket type connectors (15). The current detection module (16) is composed of three circuits. Before transferred to the processing module (17), the analogue voltage signal received from each current sensor (7) is filtered by the filter (8), amplified by the amplifier (9) and averaged by the integrator (10).

In order to involve possible frequencies that may put human life at risk in the system, there's a filter (8) selected for eliminating the current signals below 1kHz in the analogue voltage signal received from the RC low pass sensor (7) before transferred to the processing module (17). This filter (8) is also used to eliminate the magnetic statics causing faulty assessment. The filter (8) is composed of two combined quad op-amp IC units. The components of the filter (8) are selected for 1kHz low pass frequency limit. The filtered voltage signal is amplified by an amplifier (9) which has the same components with the filter (8) circuit, meaning combined two quad op- amps.

The integrator (10) is composed of eight op-amps embedded into two quad IC to eliminate the amplified voltage signal's peaks and average it over the feeding period before transferred to the processing module (17).

2. The current processing module (17) is composed of an analogue/digital multiplexer and a microcontroller (11) and a display driver (12), a display unit (13) and a wireless signal transmitter (14).

In this application, the microcontroller (11) has a built-in analogue/digital convertor unit. The microcontroller (11) is responsible to conduct this data according to the algorithm described in Figure 2. It monitors and stores the data daily or at every end of the prespecified time and transmits it to the user. The data is transferred in an instant in excess residual currents (more than standard limit) or in short circuit type faults causing RCCB cuts.

In distribution systems with more than eight protective earthing conductors (6), an analogue/digital multiplexer can be connected to the analogue input of the microcontroller (11) as an expansion IO unit.

3. The display (13) and the wireless signal transmitter (14) that has wireless data transferring features such as bluetooth, WiFi and RFID, are responsible to display and transmit the current data both at preset times and in cases of short circuit feeder faults where current magnitude is bigger than the standard threshold setting or that causes RCCB to get activated.

4. Even though the system design presented in the invention is based on the residual current measurement that passes to the protective earthing conductors (6) with eight feeders, miscellaneous IC sets can be tacked on current detection modules (16) and processing modules (17) for distribution systems with more than eight feeders or protective earthing conductors (6).

Claims

1- The invention is about a residual current tracking apparatus in low voltage power distribution systems and its' characteristic is being composed of; a current detection module (16) and a processing module (17) embedded into the modular RCCB unit (1).

2- What's mentioned in Claim 1 is about the current detection module (16) and its' characteristic is having; at least one hall effect current sensor (7) where at least one protective earthing conductor (6) passes through and that detects residual current, a filter (8) that eliminates induced static from the close by conductives or electronic circuits or possible over-current signal peaks, at least one amplifier (9) that amplifies the conditioned voltage signals and an integrator (10) that averages the current signal before being sent to the processing module (17).

3- What's mentioned in Claim 1 is about the processing module (17) and its' characteristic is having; at least one microcontroller (11) that analyses, stores the data and compares them with the preset values, at least one analogue/digital multiplexer connected to the analogue input of the microcontroller (11), a display (13) and a wireless signal transmitter (14) that informs the user on the presets and any case of danger.

4- What's mentioned in Claim 1 or Claim 3 is about the processing module (17) and its' characteristic is having; a wireless signal transmitter (14) that informs the user in any case of danger with data transferring features such as bluetooth, WiFi or RFID. 5- The invention is a residual current tracking apparatus and method in low voltage power distribution systems and its' characteristic is being consisted of the following operation steps; detection of residual current (100) by means of each protective earthing conductor (6) sequentially passing through hall effect current sensors (7), filtering of residual current (200) by the RC active low pass band filter (8) for external electrical statics, using the amplifier (9) amplifying the analogue voltage signal (300) corresponding to the residual current, averaging the analogue voltage signal (400) corresponding to the residual current with the integrator (10), converting the averaged signals to numerical form (500) with the analogue/digital convertor, making the diagnostic tests (600) of the signals received within a specified time over the microcontroller (11), with the data displayed on the display (13) informing (700) the user with the wireless signal transmitter (14) about a danger when signals exceed the preset values, initiating a new process order (800) following information and after the time specified by the user, the microcontroller (11) stopping the process (900) in a case of danger such as detection of a short circuit fault passing through any one of the protective earthing conductors (6), the display (13) displaying the number of the faulty feeder (100) and warning the user (1100) for the short circuit fault.