WO2017130051A1 - Safety arrangement for a ring main unit - Google Patents

Safety arrangement for a ring main unit Download PDF

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Publication number
WO2017130051A1
WO2017130051A1 PCT/IB2017/000032 IB2017000032W WO2017130051A1 WO 2017130051 A1 WO2017130051 A1 WO 2017130051A1 IB 2017000032 W IB2017000032 W IB 2017000032W WO 2017130051 A1 WO2017130051 A1 WO 2017130051A1
Authority
WO
WIPO (PCT)
Prior art keywords
chamber
safety arrangement
gas
ring main
main unit
Prior art date
Application number
PCT/IB2017/000032
Other languages
French (fr)
Inventor
Islam Fakhri MOHD
Original Assignee
Dubai Electricity And Water Authority
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dubai Electricity And Water Authority filed Critical Dubai Electricity And Water Authority
Priority to GB1708988.9A priority Critical patent/GB2550497B/en
Publication of WO2017130051A1 publication Critical patent/WO2017130051A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/20—Interlocking, locking, or latching mechanisms
    • H01H9/22—Interlocking, locking, or latching mechanisms for interlocking between casing, cover, or protective shutter and mechanism for operating contacts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02—Details
    • H01H33/53—Cases; Reservoirs, tanks, piping or valves, for arc-extinguishing fluid; Accessories therefor, e.g. safety arrangements, pressure relief devices
    • H01H33/56—Gas reservoirs
    • H01H33/563—Gas reservoirs comprising means for monitoring the density of the insulating gas
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
    • H02B13/00—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle
    • H02B13/02—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle with metal casing
    • H02B13/035—Gas-insulated switchgear
    • H02B13/065—Means for detecting or reacting to mechanical or electrical defects

Definitions

  • the invention relates to a safety arrangement for a Ring Main Unit (RMU) in an electrical power distribution system.
  • RMU Ring Main Unit
  • Ring Main Units or other (sub) stations are used for distributing electrical power.
  • Those RMUs usually comprise a one or more switches in order to connect or disconnect one or more feeders of the RMU. Because of the high voltages involved, part of these switches may be surrounded by isolating gasses, such as SF6. Operating these switches may only be safe when a sufficient amount of isolating gas is present, i.e. when the gas pressure is above a certain level. Therefore, a gas pressure sensor may be provided to measure the amount of isolating gas, as a safety arrangement. On the operating panel of the RMU, the switches may be operated by a user or operator.
  • a display connected to the gas pressure sensor may be provided for informing the user about the gas pressure.
  • the user may decide not to operate the switches. However, the user may overlook the display, or ignore its information.
  • the display may be faulty, i.e. it may be defective or it may show incorrect information. In these cases, the user may operate one or more switches of the RMU under unsafe conditions.
  • the object of the invention is to provide an improved safety arrangement for a Ring Main Unit.
  • the object of the invention is met by providing a safety arrangement for a ring main unit (RMU) in an electrical power distribution system, wherein the ring main unit comprises:
  • a chamber arranged for containing an isolating gas; a gas pressure sensor arranged for measuring a pressure of said isolating gas in said chamber and providing a signal indicating that the measured pressure is below a predetermined value;
  • an electrical switch which is partly accommodated in said chamber and comprises an operating element to be operated by a user, preferably from outside the chamber,
  • safety arrangement comprises
  • a blocking element arranged for blocking access to said operating element when activated
  • a control unit arranged for activating said blocking element in response to said signal.
  • the ring main unit may be operable at the following voltages: 22 kV, 11 kV or 6.6 kV.
  • the isolating gas may be SF6.
  • the electrical switch may be a mechanical electrical switch.
  • the electrical switch may be a load break switch or an isolator switch.
  • the blocking element may be a mechanical shutter or interlock.
  • the gas pressure sensor may also be arranged for providing another signal when the measured pressure is above another pre-defined value.
  • This control unit may also be arranged for activating said blocking element in response to said other signal.
  • the electrical switch comprises an operating slot providing access to said operating element, wherein said ring main unit preferably further comprises an operating handle arranged for being inserted into said slot and for engaging therein with said operating element; and said blocking element comprises shutter arranged for closing off said slot.
  • said control unit comprises a coil and a latch, wherein said coil is arranged for moving said latch from a protracted state to a retracted state when energized.
  • the latch In a protracted state, the latch is arranged for holding the blocking element in a non-blocking position, in which the operating element is accessible.
  • the latch In a retracted state, the latch is arranged for letting the blocking element fall or slide in a blocking position, in which access to the operating element is blocked.
  • said control unit further comprises a relay for energizing said coil and the gas pressure sensor comprises is electrically connected with a power source and with a relay input of said relay and wherein said pressure switch is arranged for connecting said power source with said relay input when the pressure of said gas is below said pre-determined value.
  • said relay comprises an output for a supervisory control and data acquisition (SCADA) control system.
  • a ring main unit (RMU) for an electrical power distribution system comprising:
  • a chamber arranged for containing an isolating gas
  • a gas pressure sensor arranged for measuring a pressure of said gas in the chamber and for providing a signal indicating that the measured pressure is below a pre-determined value
  • an electrical switch which is partly accommodated in said chamber and comprises an operating element to be operated by a user, preferably from outside the chamber.
  • Fig. 1 shows a schematic overview of an embodiment of the safety arrangement according to the invention, wherein the blocking element is in the non-blocking position;
  • Fig. 2 shows a schematic overview of the safety arrangement of Figure 1 , wherein the blocking element is in the blocking position.
  • RMU ring main units
  • switches may be load break switches or isolator switches or any other kind of electrical switch. Since the RMU's may operate at voltages in the range of 5 - 25 kV, the (mechanical) switches may be placed in environment with an isolating gas. Thus, a part of these switches may be arranged in chamber with an isolating gas, such as SF8.
  • any other electrical distribution (sub) station may be used and the same features as described in this document may applicable to them.
  • the switching of these switches may be performed manually by a user or operator, for example with a handle.
  • the handle may be removable from the RMU.
  • the operator may have to engage or couple the handle with an operating element of the switch.
  • the engage surface of the operating element, with which the handle is to engage may be arranged in an opening or in a slot in the operating panel of the RMU.
  • the handle needs to be inserted into the slot or opening for engaging or coupling with the operating element of the switch. After coupling, the operator may move or rotate to handle to operate the switch.
  • Figures 1 and 2 show a schematic overview of an embodiment of the safety arrangement.
  • the front view in the right corner shows the slot in the operating panel of the RMU.
  • the handle needs to be inserted in that slot for the operator to be able to operate the switch (not depicted in the figures).
  • a blocking element A is arranged in the non-blocking position, in which the slot is visible for the operator and accessible.
  • the blocking element may be made of a metal, i.e. steel or any other hard material.
  • the blocking element A is being kept in its non-blocking position by a latch L.
  • the latch L is in that case in its protracted position.
  • the blocking element A may be resting on latch L.
  • the blocking element A may be a (mechanical) shutter.
  • a pressure switch PS is depicted.
  • the pressure switch is arranged for measuring the pressure of the isolating gas in the chamber and for providing a signal indicating that the pressure is below a pre-defined value.
  • any other gas pressure sensor may be used.
  • a gas pressure sensor may comprise such a pres- sure switch or may be such a pressure switch.
  • the pressure switch may be connected to a power source, for example one providing 230 V AC.
  • the 230 V AC connection may be provided from the Low Voltage side of the same RMU.
  • a DC battery may be provided as a power source.
  • the pressure switch may be connected to a relay input of a relay.
  • the signal provided by the pressure switch may be a voltage to activate the relay.
  • the relay is arranged for energising a coil, which may at least partly surround latch L. The coil is arranged for moving said latch L from a protracted position (in figure 1 ) to a retracted position (in figure 2).
  • the relay When the pressure switch measures or detects a pressure below the pre-defined value, the relay energises the coil and the latch L is retracted. Without the latch L, blocking element A falls and enters its blocking position (see figure 2).
  • the blocking element A is arranged in the blocking position, in which the slot is invisible for the operator and inaccessible. Instead the operator sees a side of the blocking element A.
  • This side may comprise a warming text for the operator indicating that the gas pressure is too low in order to safely operate the switch. For example: "NOT SAFE TO OPERATE. GAS IS LOW".
  • the relay may comprise an output for a supervisory control and data acquisition (SCADA) control system.
  • SCADA supervisory control and data acquisition
  • RMU are provided with a gas pressure sensor that can provide a signal indicating that the gas pressure is below a pre-defined value. Furthermore, most RMU are provided with a slot that provides access to the operating element of an electrical switch. Therefore, the safety arrangement according to described embodiments can easily be assembled or mounted on an existing RMU.
  • the safety arrangement comprises a blocking element and a control element.
  • the control element may comprise a relay, a coil and a latch.

Landscapes

  • Gas-Insulated Switchgears (AREA)

Abstract

A safety arrangement for a ring main unit (RMU) in an electrical power distribution system and a ring main unit is provided. The ring main unit comprises a chamber arranged for containing an isolating gas, a gas pressure sensor arranged for measuring a pressure of said gas in the chamber and providing a signal indicating that the measured pressure is below a predetermined value, and an electrical switch, which is partly accommodated in said chamber and comprises an operating element to be operated by a user. The safety arrangement comprises a blocking element arranged for blocking access to said operating element when activated, and a control unit arranged for activating said blocking element in response to said signal.

Description

Safety arrangement for a ring main unit
DESCRIPTION
FIELD OF THE INVENTION
The invention relates to a safety arrangement for a Ring Main Unit (RMU) in an electrical power distribution system.
BACKGROUND OF THE INVENTION
In many electrical power distribution systems Ring Main Units or other (sub) stations are used for distributing electrical power. Those RMUs usually comprise a one or more switches in order to connect or disconnect one or more feeders of the RMU. Because of the high voltages involved, part of these switches may be surrounded by isolating gasses, such as SF6. Operating these switches may only be safe when a sufficient amount of isolating gas is present, i.e. when the gas pressure is above a certain level. Therefore, a gas pressure sensor may be provided to measure the amount of isolating gas, as a safety arrangement. On the operating panel of the RMU, the switches may be operated by a user or operator.
A display connected to the gas pressure sensor may be provided for informing the user about the gas pressure. When the gas pressure is too low, the user may decide not to operate the switches. However, the user may overlook the display, or ignore its information. Furthermore, the display may be faulty, i.e. it may be defective or it may show incorrect information. In these cases, the user may operate one or more switches of the RMU under unsafe conditions.
OBJECT OF THE INVENTION
Therefore, the object of the invention is to provide an improved safety arrangement for a Ring Main Unit.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is met by providing a safety arrangement for a ring main unit (RMU) in an electrical power distribution system, wherein the ring main unit comprises:
a chamber arranged for containing an isolating gas; a gas pressure sensor arranged for measuring a pressure of said isolating gas in said chamber and providing a signal indicating that the measured pressure is below a predetermined value;
an electrical switch, which is partly accommodated in said chamber and comprises an operating element to be operated by a user, preferably from outside the chamber,
wherein the safety arrangement comprises
a blocking element arranged for blocking access to said operating element when activated; and,
a control unit arranged for activating said blocking element in response to said signal. With this safety arrangement, the user or operator cannot operate the switches when the amount of gas is insufficient for safe operation, because in that case, access to the switch is blocked by the blocking element. Thus, even if the operator ignores, misinterprets or is misinformed by a displayed gas pressure, he cannot operate the switches. This improves the safety of operating the RMU.
The ring main unit may be operable at the following voltages: 22 kV, 11 kV or 6.6 kV.
The isolating gas may be SF6. The electrical switch may be a mechanical electrical switch. The electrical switch may be a load break switch or an isolator switch. The blocking element may be a mechanical shutter or interlock.
The gas pressure sensor may also be arranged for providing another signal when the measured pressure is above another pre-defined value. This control unit may also be arranged for activating said blocking element in response to said other signal.
According to another embodiment of the safety arrangement according to the invention, the electrical switch comprises an operating slot providing access to said operating element, wherein said ring main unit preferably further comprises an operating handle arranged for being inserted into said slot and for engaging therein with said operating element; and said blocking element comprises shutter arranged for closing off said slot.
According to another embodiment of the safety arrangement according to the invention, said control unit comprises a coil and a latch, wherein said coil is arranged for moving said latch from a protracted state to a retracted state when energized. In a protracted state, the latch is arranged for holding the blocking element in a non-blocking position, in which the operating element is accessible. In a retracted state, the latch is arranged for letting the blocking element fall or slide in a blocking position, in which access to the operating element is blocked.
According to another embodiment of the safety arrangement according to the invention, said control unit further comprises a relay for energizing said coil and the gas pressure sensor comprises is electrically connected with a power source and with a relay input of said relay and wherein said pressure switch is arranged for connecting said power source with said relay input when the pressure of said gas is below said pre-determined value. According to another embodiment of the safety arrangement according to the invention, said relay comprises an output for a supervisory control and data acquisition (SCADA) control system.
According to another aspect of the invention, a ring main unit (RMU) for an electrical power distribution system is provided, comprising:
a chamber arranged for containing an isolating gas;
a gas pressure sensor arranged for measuring a pressure of said gas in the chamber and for providing a signal indicating that the measured pressure is below a pre-determined value;
- an electrical switch, which is partly accommodated in said chamber and comprises an operating element to be operated by a user, preferably from outside the chamber.
a safety arrangement according to any of embodiments described in this document.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
For a more complete understanding of the present invention, reference is established to the following description made in connection with accompanying drawings in which:
Fig. 1 shows a schematic overview of an embodiment of the safety arrangement according to the invention, wherein the blocking element is in the non-blocking position; and,
Fig. 2 shows a schematic overview of the safety arrangement of Figure 1 , wherein the blocking element is in the blocking position.
DETAILED DESCRIPTION OF THE INVENTION
Many power distribution systems comprise so called ring main units (RMU). Inside the RMUs, one or more mechanical switches may be arranged between different feeders of the RMUs. These switches may be load break switches or isolator switches or any other kind of electrical switch. Since the RMU's may operate at voltages in the range of 5 - 25 kV, the (mechanical) switches may be placed in environment with an isolating gas. Thus, a part of these switches may be arranged in chamber with an isolating gas, such as SF8.
Instead of an RMU, any other electrical distribution (sub) station may be used and the same features as described in this document may applicable to them.
The switching of these switches may be performed manually by a user or operator, for example with a handle. The handle may be removable from the RMU. In order to operate the switch the operator may have to engage or couple the handle with an operating element of the switch. The engage surface of the operating element, with which the handle is to engage, may be arranged in an opening or in a slot in the operating panel of the RMU. Thus, the handle needs to be inserted into the slot or opening for engaging or coupling with the operating element of the switch. After coupling, the operator may move or rotate to handle to operate the switch.
Figures 1 and 2 show a schematic overview of an embodiment of the safety arrangement. The front view in the right corner shows the slot in the operating panel of the RMU. The handle needs to be inserted in that slot for the operator to be able to operate the switch (not depicted in the figures).
In figure 1 , a blocking element A is arranged in the non-blocking position, in which the slot is visible for the operator and accessible. The blocking element may be made of a metal, i.e. steel or any other hard material.
The blocking element A is being kept in its non-blocking position by a latch L. The latch L is in that case in its protracted position. The blocking element A may be resting on latch L. The blocking element A may be a (mechanical) shutter.
On the left side of figures 1 and 2, a pressure switch PS is depicted. The pressure switch is arranged for measuring the pressure of the isolating gas in the chamber and for providing a signal indicating that the pressure is below a pre-defined value. Instead of a pressure switch any other gas pressure sensor may be used. A gas pressure sensor may comprise such a pres- sure switch or may be such a pressure switch.
The pressure switch may be connected to a power source, for example one providing 230 V AC. The 230 V AC connection may be provided from the Low Voltage side of the same RMU. As an alternative, a DC battery may be provided as a power source.
The pressure switch may be connected to a relay input of a relay. The signal provided by the pressure switch may be a voltage to activate the relay. The relay is arranged for energising a coil, which may at least partly surround latch L. The coil is arranged for moving said latch L from a protracted position (in figure 1 ) to a retracted position (in figure 2).
When the pressure switch measures or detects a pressure below the pre-defined value, the relay energises the coil and the latch L is retracted. Without the latch L, blocking element A falls and enters its blocking position (see figure 2).
In figure 2, the blocking element A is arranged in the blocking position, in which the slot is invisible for the operator and inaccessible. Instead the operator sees a side of the blocking element A. This side may comprise a warming text for the operator indicating that the gas pressure is too low in order to safely operate the switch. For example: "NOT SAFE TO OPERATE. GAS IS LOW".
The relay may comprise an output for a supervisory control and data acquisition (SCADA) control system. In that way, also the control system of the RMU or (parts of) the elec- trical power distribution system can also be informed that the switches can be operated, because the pressure of the isolating gas is insufficient for safe operation.
Most RMU are provided with a gas pressure sensor that can provide a signal indicating that the gas pressure is below a pre-defined value. Furthermore, most RMU are provided with a slot that provides access to the operating element of an electrical switch. Therefore, the safety arrangement according to described embodiments can easily be assembled or mounted on an existing RMU.
In general, the safety arrangement according to the invention comprises a blocking element and a control element. The control element may comprise a relay, a coil and a latch.
While the present inventions have been described and illustrated in conjunction with a number of specific embodiments, those skilled in the art will appreciate that variations and modifications may be made without departing from the principles of the inventions as herein illustrated, as described and claimed. The present inventions may be embodied in other spe-cific forms without departing from their spirit or essential characteristics. The described em-bodiments are considered in all respects to be illustrative and not restrictive. The scope of the inventions is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalence of the claims are to be embraced within their scope.

Claims

1. Safety arrangement for a ring main unit (RMU) in an electrical power distribution sys- tern, wherein the ring main unit comprises:
a chamber arranged for containing an isolating gas;
a gas pressure sensor arranged for measuring a pressure of said isolating gas in the chamber and providing a signal indicating that the measured pressure is below a predetermined value; and,
- an electrical switch, which is partly accommodated in said chamber and comprises an operating element to be operated by a user from outside the chamber,
wherein the safety arrangement comprises:
a blocking element (A) arranged for blocking access to said operating element when activated; and,
- a control unit arranged for activating said blocking element (A) in response to said signal.
2. Safety arrangement according to claim 1 , wherein:
- the electrical switch comprises an operating slot providing access to said operating element;
- said ring main unit preferably further comprises an operating handle arranged for being insert- ed into said slot and for engaging therein with said operating element; and
- said blocking element comprises shutter arranged for closing off said slot.
3. Safety arrangement according to claim 1 or 2, wherein:
- said control unit comprises a coil and a latch (L);
- said coil is arranged for moving said latch (L) from a protracted state towards a retracted state when energized;
- in a protracted state, the latch (L) is arranged for holding the blocking element (A) in a non- blocking position, in which the operating element is accessible; and,
- in a retracted state, the latch (L) is arranged for letting the blocking element (A) fall in a block- ing position, in which access to the operating element is blocked.
4. Safety arrangement according to any of claims 1-3, wherein:
- said control unit further comprises a relay for energizing said coil;
- the gas pressure sensor is electrically connected with a power source and with a relay input of said relay;
- said pressure switch is arranged for connecting said power source with said relay input when the pressure of said gas is below said pre-determined value.
5. Safety arrangement according to any of claims 1-4, wherein said relay comprises an output for a supervisory control and data acquisition (SCADA) control system.
6. Ring main unit (RMU) for an electrical power distribution system is provided, comprising:
a chamber arranged for containing an isolating gas;
a gas pressure sensor arranged for measuring a pressure of said gas in said chamber and for providing a signal indicating that measured pressure is below a pre-determined value; - an electrical switch, which is partly accommodated in said chamber and comprises an operating element to be operated by a user from outside the chamber; and,
a safety arrangement according to any of claims 1-5.
PCT/IB2017/000032 2016-01-25 2017-01-25 Safety arrangement for a ring main unit WO2017130051A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1708988.9A GB2550497B (en) 2016-01-25 2017-01-25 Safety arrangement for a ring main unit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AE852016 2016-01-25
AEP85/2016 2016-01-25

Publications (1)

Publication Number Publication Date
WO2017130051A1 true WO2017130051A1 (en) 2017-08-03

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ID=59397488

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2017/000032 WO2017130051A1 (en) 2016-01-25 2017-01-25 Safety arrangement for a ring main unit

Country Status (1)

Country Link
WO (1) WO2017130051A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN201781221U (en) * 2010-09-06 2011-03-30 北京合纵实科电力科技有限公司 Low-air pressure latching unit for ring main units and ring main unit adopting same
CN204178965U (en) * 2014-05-12 2015-02-25 国家电网公司 The safety interlock system of 10kV ring main unit and off-tube Ore-controlling Role

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN201781221U (en) * 2010-09-06 2011-03-30 北京合纵实科电力科技有限公司 Low-air pressure latching unit for ring main units and ring main unit adopting same
CN204178965U (en) * 2014-05-12 2015-02-25 国家电网公司 The safety interlock system of 10kV ring main unit and off-tube Ore-controlling Role

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