GB2620205A

GB2620205A - Electrical protection system

Info

Publication number: GB2620205A
Application number: GB2209743.0A
Authority: GB
Inventors: Howe Smith Leland; Brodie Charlie; De Filippi Roland; Comins Todd
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2022-06-27
Filing date: 2022-07-01
Publication date: 2024-01-03
Also published as: GB202209743D0; GB202209385D0

Abstract

The electrical protection system has a PEN relay 40 for selectively breaking a PE conductor 21; an L relay 30-1 for selectively breaking an L conductor; and an N relay 30-2 for selectively breaking an N conductor. A comparator 50 compares the potential difference between the L conductor and the N conductor with a predetermined safety criterion and issues a fault signal when the predetermined safety criterion is not met. A relay control circuit is operationally connected to the comparator to receive the fault signal, and cause the PE relay, the L relay, and the N relay to open after receiving the fault signal thereby selectively breaking the PE conductor, the L conductor, and the N conductor. The protection system may be used in an EV charging system.

Description

ELECTRICAL PROTECTION SYSTEM

FIELD OF THE INVENTION

The present invention relates to an electrical protection system for selectively breaking a connection between an electric supply and an electric consumer or a socket connectable to the electric consumer.

BACKGROUND TO THE INVENTION

In some regulations, electrical vehicle charging using a protective multiple earth (PME) power supply system is permitted, without providing an Earth rod, as long a suitable protective earth / neutral (PEN) fault breaker is provided instead. Various PEN fault detection solutions are available.

One example is disclosed in GB2574338A. This system employs a data processing arrangement which determines a voltage (potential difference) between live and neutral conductors, and switches a switching matrix arrangement to disconnect the live, neutral, and earth conductors from an electrical apparatus in the event that the potential difference The example of GB2574338A is potentially sensitive to malfunctions, as it relies on a computerized device to execute the functionality described above. Moreover, the system is not compliant with all relevant regulations.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided an electrical protection system for selectively breaking a connection between an electric supply and an electric consumer or a socket connectable to the electric consumer, wherein the electric supply comprises: -a protective earth (PE) terminal connected to a PE conductor; and -an electric power source comprising a neutral (N) terminal connected to an N conductor, and a live (L) terminal connected to an L conductor; wherein the PE conductor, the N conductor, and the L conductor each extend between the electric supply and the electric consumer or the socket; and wherein the electrical protection system comprises: -a PE relay in the PE conductor for selectively breaking the PE conductor; -an L relay in the L conductor for selectively breaking the L conductor; -an N relay in the N conductor for selectively breaking the N conductor; -a comparator arranged to compare a potential difference between the L conductor and the N conductor with a predetermined safety criterion and to issue a fault signal when the predetermined safety criterion is not met; -a relay control circuit operationally connected to the comparator to receive the fault signal, which relay control circuit is arranged to cause the PE relay, the L relay, and the N relay to open after receiving the fault signal thereby selectively breaking the PE conductor, the L conductor, and the N conductor.

Several improvements can be made to this system, as will be described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accordance with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements Fig. 1 shows a schematic block diagram of an electrical protection system suitable for a single-phase charger; Fig. 2 shows a schematic block diagram of a PEN detection unit.

DETAILED DESCRIPTION OF THE INVENTION

The person skilled in the art will readily understand that, while the detailed description of the invention will be illustrated making reference to one or more embodiments, each having specific combinations of features and measures, many of those features and measures can be equally or similarly applied independently in other embodiments or combinations.

The present invention proposes several improvements which can be applied to an electrical protection system for selectively breaking a connection between an electric supply and an electric consumer or a socket connectable to the electric consumer. Typically, the electric consumer is a battery system of an electric vehicle. The electrical protection system may suitably be used in combination with and/or integrated with an electric vehicle charging system.

The electrical protection system generally has a PE relay for selectively breaking a PE conductor; an L relay for selectively breaking an L conductor; and an N relay for selectively breaking an N conductor. A comparator is arranged to compare a potential difference between the L conductor and the N conductor with a predetermined safety criterion and to issue a fault signal when the predetermined safety criterion is not met. A relay control circuit is operationally connected to the comparator to receive the fault signal, which relay control circuit is arranged to cause the PE relay, the L relay, and the N relay to open after receiving the fault signal thereby selectively breaking the PE conductor, the L conductor, and the N conductor.

For example, the comparator and the relay control circuit may be fully analogue devices. This is referred to as a hardware controlled safety device. This is found to be more robust and reliable compared to when a computerized element is needed for the opening of the relays in response to the safety criterion not being met. Also, such analogue devices are readily auditable as opposed to computer controlled execution, which would require inspection of the underlying code.

Moreover, the predetermined safety criterion may comprise a window rather than a voltage threshold. A window is characterized by a lower acceptable potential difference and an upper acceptable potential difference (voltage). This protects both against a PEN fault as well as against damaging the electric consumer by operating it at a too high voltage.

The comparator and the relay control circuit may preferably be operationally connected with each other via an optocoupler unit, a transformer or any other electrically isolating signal coupler. This allows for communicating the fault signal to the relay control unit by so as to keep the secondary circuit electrically separated from the primary circuit. Preferably, the relay control circuit may comprise a time-delay circuit to impose a limited time delay between first receiving the fault signal and causing the PE relay, the L relay, and the N relay to open. Herewith, premature opening of the relays during short dips and interniptions in the L conductor can be mitigated. The limited time delay should be consistent with any locally applicable regulation. For example, limited time delay may be in a range of from 1.0 second to 5.0 second, preferably from 1.0 second to 4.5 second, and more preferably from 3.5 second to 4.5 second.

In preferred embodiments, the L relay and the N relay are independently switchable from the PE relay. The L relay and the N relay may for example combined in a single AC relay of at least double pole type, wherein one pole is reserved for the L conductor and one pole is reserved for the N conductor. In case of multi-phase systems, additional poles may be reserved for additional phases. The AC relay may be connected to an AC relay driver via an AC relay driver line, to supply an AC relay driver signal to selectively close the AC relay. An AC relay driver line relay may be provided in the AC relay driver line for selectively breaking the AC relay driver line. Interrupting the AC relay driver signal causes the AC relay to open. Preferably, the AC relay driver line relay is combined in a single PEN relay of at least double pole type with the PE power conductor. This way, the AC relay driver line breaks simultaneously with the PE conductor. Also, this provides a hard guarantee that the AC relay cannot be energized (and closed) unless the PEN relay is closed and the PE connected. However, by having a separate AC relay, it is possible to voluntarily break or close the L and N conductors while the PE conductor remains closed.

Alternatively, if the L relay and the N relay are not combined in a single relay common to both, then each of the individual driver lines for the L relay and the N relay may be passed through the PEN relay to accomplish that the L relay and the N relay can never be closed when the PEN relay is open. Still alternatively, in case the L relay and the N relay are not combined in a single relay, both relays could be driven by a common driver similar to the AC driver and the AC relay driver line described above. However, the common AC relay variant is preferred, as it offers fewer components that can fail.

A micro-controller unit (MCU) may be provided for performing several functions The MCU may generally involve computer readable instructions which, when executed in the MCU, may provide additional functionality. A metrology unit may be configured to digitize the potential difference between the L conductor and the N conductor. The MCC may be configured to receive digitized potential difference. The &ICU may suitably comprise an alert output. An alert signal may be activated on the alert output, in response to the digitized potential difference. Also, the digitized potential difference may be monitored to ensure that the electrical protection system is functioning correctly.

Furthermore, the MCU may comprise wireless or wired communication with one or more user interface devices. For instance, the MCU may enabled to connect to a user interface that can be run on a mobile device such as a tablet or smart phone, for instance by internet connectivity and/or Bluetooth. The MCU may further connect to the AC relay driver and/or PEN relay driver, to override the PEN fault detection signals initiated by the comparator. These connections may further assist to reset the system after having caused the PE relay, the L relay, and the N relay to open.

If desired, the MCU may be employed to continuously monitor the state of PEN fault. The MCU may be employed to isolate the conductors and/or report a hardware malfunction, and/or disabling future use sessions until the electrical protection system has been serviced, whenever a PEN fault is detected by the MCU, which last longer than any predetermined delay time, while the MCU also detects that the hardware control has failed to cause the relays to open With the increase of renewable energy, it is often the case that the L to N voltage will go out of range when renewables come on-or off-line. Analytics can be employed in a monitoring unit, which may be integrated in the MCU or a separate monitoring unit, to predict when these voltage excursions will occur, enabling the system to adapt its charge cycle to avoid these events. If the system is not charging during a PEN fault event, but the charging system is forced to shut down due to a PEN fault, it may be acceptable to restart the charge session automatically because the fault never triggered a shutdown.

The monitoring unit may be arranged to cause a controlled shutdown of electric consumer activity before PEN fault occurring and associated triggering opening the PE relay. Herewith a user initiated reset can be avoided. The monitoring unit might employ analsdics of wider grid heuristics to predict such times.

These improvements and features summarized above may each be applied separately, or in various combinations of one or more of these improvements and features.

Referring now to Fig. 1, there is shown a schematic block diagram of an electrical protection system suitable for a single-phase charger. On the right is depicted an electric supply 10 and on the tight an electric consumer cable or a socket connectable to the electric consumer (20). The electric supply 10 is provided with a protective earth (PE) terminal 11 connected to a PE conductor 21; a neutral (N) terminal 12 connected to an N conductor 22; and a live (L) terminal 13 connected to an L conductor 23. The PE conductor 21, the N conductor 22, and the L conductor each extend between the electric supply 10 and the electric consumer or the socket 20.

The electrical protection system further comprises an AC relay 30. This is preferably a multi-pole single throw relay. An AC relay first pole 30-1 represents an N relay for selectively breaking the N conductor 22, and an AC relay second pole 30-2 represents an L relay for selectively breaking the L conductor 23. For a single phase system, a double-pole AC relay may suffice. The AC relay 30 is connected to an AC relay driver 35,via an AC relay driver line 36, to supply an AC relay driver signal to selectively close the AC relay 30 by energizing the AC relay 30. Preferably, the AC relay 30 is a fail-open relay, meaning that it inherently opens when not energized. -5

The electrical protection system further comprises a PEN relay 40, which may be provided as a double pole single throw relay. A PEN relay first pole 40-1 represents a PE relay, for selectively breaking the PE conductor 21. A PEN relay second pole 40-2 represents an AC relay driver line relay, which is arranged to break the AC relay driver line 36 when the PE relay selectively breaks the PE conductor 21. The PEN relay 40 is connected to a PEN relay driver 45,via a PEN relay driver line 46. A PEN relay driver signal may be provided to selectively close the PEN relay 40 by energizing the PEN relay 40. Preferably, the PEN relay 40 is a fail-open relay, meaning that it inherently opens when not energized.

The PEN relay driver 45 is controlled by a PEN detection unit 50, which is further detailed in Fig. 2. The PEN detection unit 50 comprises a comparator 52. It is arranged to compare a potential difference between the L conductor 23 and the N conductor 22 with a predetermined safety criterion. To this end, the AC voltage may suitably be rectified using a bridge, and then fed as input to a window detector IC. A voltage divider may be employed to provide a lower reference voltage and an upper reference voltage to the window detector IC. The lower reference voltage and upper reference voltage represent a predetermined safety criterion, which relates directly to a lower acceptable potential difference and an upper acceptable potential difference between the L conductor 23 and the N conductor 22. In one embodiment, the lower acceptable potential difference is 207 Vrms and the upper acceptable potential difference is 253 Vrms. However, depending on local grid specifications, other values may be selected. The window detector IC issues a fault signal, when the predetermined safety criterion is not met, i.e. when the L-N potential difference is lower than the lower acceptable potential difference or higher than the upper acceptable potential difference.

The fault signal may be passed to a relay control circuit 54, which is operationally connected to the comparator 52 via an optocoupler 56. The relay control circuit 54 controls the PEN relay driver 45. A delay circuit is included in the relay control circuit 54, which imposes a limited delay time (for example set to 4.0 sec) between the start of the fault signal and issuance of a PEN relay driver control signal, which would open the PEN relay 40. This is to eliminate the opening of the PEN relay 40 during short dips and interruptions in the AC power. However, when the fault signal sustains for longer than the limited delay time, the PEN relay 40 is opened, whereby disconnecting (breaking) the PE terminal 11 from the electricity consumer. Simultaneously, the AC relay driver line 36 is broken by the opening of the PEN relay 40, resulting in opening of the AC relay 30. This disconnects the L and N terminals 12,13 from the electricity consumer.

Referring again to Fig. 1, there is further provided a micro-controller unit (MCU) 60. Furthermore, a metrology unit 70 may be provided. The metrology unit 70 may be configured to digitize the potential difference between the L conductor 13 and the N conductor 12.

Furthermore, the MCU may comprise interne connectivity and/or Blue tooth, to connect to a user interface that can be run on a mobile device, such as a tablet or smart phone.

The NICU 60 may employ a software backup system, to monitor the hardware PEN detection unit 50, to ensure that it is functioning correctly. The MCU 60 may also assist to reset the system after a fault detection event has occurred. The MCU 60 may receive one or more of AC relay status 37, PEN relay status 47, the digitized potential difference 77 from the metrology unit 70. Moreover, the MCU may issue one or more of an AC relay control signal 38, a PEN relay control signal 48, and an alert signal 68. The PEN relay control signal 48 feeds into the PEN relay driver 45 via an AND gate. By this, the PEN relay 40 is only energized conditionally upon the PEN detection unit does not issue a fault signal and the MCU issues the permissive.

For example, when either or both of the AC relay 30 and the PEN relay 40 opens, the MCU 60 will detect this through the AC relay status 37 and PEN relay status 47, and immediately withdraw a permissive on the PEN relay control signal 48. When the L-N voltage restores within the safety criterion, then the fault signal from the PEN detection unit 50 can be withdrawn immediately (with no delay). However, the permissive to the PEN relay must be reasserted as well before the PEN relay 40 can close again.

The PEN permissive is held disabled until one of the following user initiated actions occurs: 1. a user disconnects the electric consumer (such as the electric vehicle) under charge (this option applies to socketed units); 2. the user activates a reset function, for example on an app running on the mobile device or by pressing a hardware reset button on the system (if provided).

The AC relay control signal 38 can be asserted via the MCC at any time after the PEN relay 40 has been dosed.

The PEN permissive on the PEN relay control line 48 may also be employed to test the PEN relay driver 45 and the PEN relay 40 under circumstances that L-N potential difference satisfies the safety criterion An alert signal may be activated on the alert output 68, in response to the digitized potential difference from the metrology unit 80 indicating that the safety criterion is not met or in case there is another malfunction. Also, the digitized potential difference may be monitored to ensure that the electrical protection system is functioning correctly.

The electrical protection system may further comprise a standard residual current device (RCD) 80. The RCD generally determines a current differential between L current and N current, and it trips if more than a threshold current leaks from L to ground.

The invention has been illustrated by means of a single phase system. It may be extended to multiple-phase system by for example employing a quad pole type relay for the AC relay, whereby each additional L phase employs an additional pole compared to what is shown in Fig. 1. Also, each phase would preferably be connected to its own PEN detection unit 50. However, the output of each phase' s PEN detection unit can be channeled to a unitary PEN relay driver 45 via a multiple input AND device. The effect of the AND device is that the PEN relay 40 is closed if at least one of the PEN detection units issues a fault signal.

The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims.

Claims

CLAIMS1. An electrical protection system for selectively breaking a connection between an electric supply and an electric consumer or a socket connectable to the electric consumer, wherein the electric supply comprises: -a protective earth (PE) terminal connected to a PE conductor; and -an electric power source comprising a neutral (N) terminal connected to an N conductor, and a live (L) terminal connected to an L conductor; wherein the PE conductor, the N conductor, and the L conductor each extend between the electric supply and the electric consumer or the socket; and wherein the electrical protection system comprises: -a PE relay in the PE conductor for selectively breaking the PE conductor; -an L relay in the L conductor for selectively breaking the L conductor; -an N relay in the N conductor for selectively breaking the N conductor; -a comparator arranged to compare a potential difference between the L conductor and the N conductor with a predetermined safety criterion and to issue a fault signal when the predetermined safety criterion is not met; -a relay control circuit operationally connected to the comparator to receive the fault signal, which relay control circuit is arranged to cause the PE relay, the L relay, and the N relay to open after receiving the fault signal thereby selectively breaking the PE conductor, the L conductor, and the N conductor.
2. The electrical protection system of claim 1, wherein the comparator is an analogue device.
3. The electrical protection system of claim 1 or 2, wherein the predetermined safety criterion comprises a window characterized by a lower acceptable potential difference and an upper acceptable potential difference.
4. The electrical protection system of any one of the preceding claims, wherein the comparator and the relay control circuit are operationally connected with each other via an optocoupler unit.
5. The electrical protection system of any one of the preceding claims, wherein the relay control circuit comprises a time-delay circuit to impose a limited time delay between first receiving the fault signal and causing the PE relay, the L relay, and the N relay to open.
6. The electrical protection system of any one of the preceding claims, wherein the L relay and the N relay are independently switchable from the PE relay.
7. The electrical protection system of claim 6, wherein the L relay and the N relay are connected to at least one relay driver via at least one relay driver line, to supply an L relay driver signal to selectively close the L relay and an N relay driver signal to selectively close the N relay, the electrical protection system further comprising a relay driver line relay in the at least one relay driver line for selectively breaking the at least one relay driver line, wherein the at least one relay driver line relay is combined with the PE relay in a single PEN relay of at least double pole type, to break the at least one relay driver line simultaneously with the PE conductor.
8. The electrical protection system of claim 7, wherein the PEN relay is connected to a PEN relay driver to supply a PEN relay driver signal to close the PEN relay, whereby the relay control circuit is operationally connected to the PEN relay driver, whereby opening of the PEN relay causes opening of the L relay and the N relay due to breaking of the at least one relay driver line.
9. The electrical protection system of claim 6, wherein the L relay and the N relay are combined in a single AC relay of at least double pole type, which AC relay is connected to an AC relay driver via an AC relay driver line, to supply an AC relay driver signal to selectively close the AC relay.
10. The electrical protection system of claim 9, the system further comprising an AC relay driver line relay in the AC relay driver line for selectively breaking the AC relay driver line, wherein the AC relay driver line relay is combined with the PE relay in a single PEN relay of at least double pole type, to break the AC relay driver line simultaneously with the PE conductor.
11. The electrical protection system of claim 10, wherein the PEN relay is connected to a PEN relay driver to supply a PEN relay driver signal to close the PEN relay, whereby the relay control circuit is operationally connected to the PEN relay driver, whereby opening of the PEN relay causes opening of the AC relay due to breaking of the AC relay driver line.
12. The electrical protection system of any one of the preceding claims, further comprising a metrology unit configured to digitize the potential difference between the L conductor and the N conductor, and an micro-controller unit (A/ICU) configured to receive digitized potential difference. -10-
13. The electrical protection system of claim 12, wherein the MCU comprises an alert output, and wherein the MCU is arranged to activate an alert signal on the alert output in response to the digitized potential difference.
14. The electrical protection system of claim 8 or 11, in combination with claim 12 or 13, wherein the MCU is configured to communicate a permissive signal to the PEN relay driver and to conditionally withdraw said permissive signal.
15. The electrical protection system of claim 14, wherein, once withdrawn, a user initiated action is required to restore the permissive signal.
16. The electrical protection system of any one of the preceding claims, further comprising a monitoring unit which is arranged to cause a controlled shutdown of electric consumer activity before PEN fault occurring and triggering opening the PE relay.
17. The electrical protection system of claim 16, wherein the monitoring unit is configured to apply analytics to wider grid heuristics to predict when a PEN fault might occur.