Fast acting disconnect system for protecting surge suppressors and connected utilization equipment from power line overvoltages

• US 6,118,639 A
• Filed: 03/29/1999
• Issued: 09/12/2000
• Est. Priority Date: 05/30/1997
• Status: Expired due to Fees

• Current Assignee: Richard Goldstein
• Original Assignee: Richard Goldstein
• Inventors: Goldstein, Richard
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/280,358
• Time in Patent Office: 533 Days
• Field of Search: 361/54, 361/55, 361/91.1, 361/93.1, 361/111, 361/119, 361/91.5, 361/91.6
• US Class Current: 361/55
• CPC Class Codes: H01H 73/44 reset by push-button, pull-knob or slide
• CPC Class Codes: H02H 9/042 comprising means to limit the absorbed power or indicate damaged over-voltage protection device

Abstract

A fast acting disconnect system is incorporated with a transient voltage surge suppressor to protect the surge suppressor and the connected utilization equipment from power frequency overvoltages. A resettable circuit breaker permits reconnection after disconnecting the AC voltage source due to a power frequency overvoltage. The system is applicable to protect equipment connected to an AC source of voltage that has a phase conductor, a neutral conductor and a grounding conductor with surge suppressors connected to protect against transient voltage surges from phase-to-neutral, phase-to-ground and neutral-to-ground. The system protects against damage of the surge suppressor and the connected equipment from power frequency overvoltages as specified for testing by a recognized testing agency. A transient voltage surge of the greatest magnitude anticipated in the environment for which the system is designed will not cause a false disconnect operation. The system will respond to a power frequency overvoltage under conditions in which it is not energized prior to the application of the overvoltage.

Claims

1. In an electrical disconnect system for protecting a transient voltage surge suppressor from power frequency overvoltages and also for protecting a load comprising utilization equipment connected thereto from said power frequency overvoltages, said system including input terminals for connection to a source of AC voltage, and output terminals for connection to said utilization equipment, surge suppressor components connected to said input terminals for clamping short duration transient voltage surges to a safe value, said surge suppressor components and said utilization equipment being capable of enduring said power frequency overvoltage for a brief period of time without damage, said system comprising:

an electrically operated switch having AC source connection terminals for connection to said source of AC voltage and load connection terminals connected to said input terminals, a resettable disconnect switch for connecting and disconnecting said AC source connection terminals from said load connection terminals, a switch operating mechanism for opening said disconnect switch when energized, to disconnect said AC source connection terminals from said load connection terminals, and a latch mechanism for resetting said disconnect switch for reconnecting said AC source connection terminals to said load terminals; and

a sense and control circuit for rapidly energizing said switch operating mechanism upon a power frequency overvoltage at said input terminals, said sense and control circuit including a capacitor and a capacitor charge circuit therefor for charging said capacitor directly from said input terminals to a disconnect switch operating voltage level which energizes said switch operating mechanism to open said disconnect switch, and a capacitor discharge switch connected between said capacitor and said switch operating mechanism to couple thereto the voltage charge on the capacitor when it reaches said disconnect switch operating voltage level,

whereby said disconnect switch disconnects said input terminals from the AC source connection terminals before the end of said brief time period during which said surge suppressor components and said utilization equipment can endure said power frequency overvoltage without damage, thereby protecting both the surge suppressor and the utilization equipment from said power frequency overvoltage.

2. The electrical disconnect system as defined in claim 1 wherein said electrically operated switch is a mechanical circuit breaker having an electromagnetically actuated disconnect switch operating mechanism and a manual resetting mechanism.

3. The electrical disconnect system as defined in claim 1 wherein said electrically operated switch is a solid state relay having an electrically isolated control section for rendering said relay non-conductive and for resetting it to a conductive state.

4. The electrical disconnect system as defined in claim 1 wherein said capacitor discharge switch is a threshold voltage triggered switch that remains in a high impedance condition to prevent energization of said disconnect switch operating mechanism until the charge on said capacitor reaches said disconnect switch operating voltage level, at which level the threshold voltage triggered switch is switched to very low impedance thereby discharging the capacitor through said switch operating mechanism.

5. The electrical disconnect system as defined in claim 4 wherein said threshold voltage triggered switch is a silicon bilateral voltage triggered switch, also known as a SIDAC, and a SIDACTOR.

6. The electrical disconnect system as defined in claim 1 wherein said sense and control circuit includes a full-wave rectifier bridge with all other sense and control circuit elements contained within the bridge, so that any sense and control circuit element is either unipolar or bipolar, whereby a power frequency overvoltage that reaches a level that is to open said disconnect switch charges said capacitor to said switch energizing level, whether said overvoltage is instantaneously positive or negative.

7. The electrical disconnect system as defined in claim 1 wherein there is connected in series with said capacitor, charge-limiting impedance such that the charge on the capacitor from said power frequency overvoltage is not reduced to less than said disconnect switch operating voltage level, but the charge from a short duration transient voltage surge is reduced to less than said disconnect switch operating voltage level.

8. The electrical disconnect system as defined in claim 7 wherein said charge-limiting impedance is an inductor.

9. The electrical disconnect system as defined in claim 7 wherein said charge-limiting impedance is a resistor.

10. The electrical disconnect system as defined in claim 7 wherein said short duration transient voltage surge is of the largest magnitude anticipated in the environment for which the system and said surge suppressor is designed.

11. The electrical disconnect system as defined in claim 6 wherein there is included in said capacitor charge circuit a threshold voltage conducting device that substantially blocks the flow of current until the breakdown voltage is applied, thereby reducing the voltage applied to the capacitor to less than the peak voltage of said source AC voltage by about the magnitude of said breakdown voltage.

12. The electrical disconnect system as defined in claim 1 wherein said source of AC voltage has a phase conductor and a neutral conductor to be connected to respective ones of said input terminals, and a grounding conductor to be connected to a desired grounding point on said utilization equipment and there is provided in said system a ground input terminal for connecting said grounding conductor to the system and a ground output terminal for connection to said grounding point on said utilization equipment, connections from said system input ground terminal and said phase and neutral input terminals to three separate surge suppressor components connected across the three pairs of input terminals involved so that all ports of the utilization equipment are surge protected thereby, and a six rectifier array connecting said input terminals to said sense and control circuit to form full-wave rectifier bridge circuits so that any sense and control circuit element is either unipolar or bipolar, whereby a power frequency overvoltage imposed on any pair of said input terminals that reaches a level that is to open said disconnect switch, charges said capacitor to said switch energizing level, whether said overvoltage is instantaneously positive or negative.

13. The electrical disconnect system as defined in claim 12 wherein said disconnect switch has two poles that simultaneously disconnect both said load terminals from said AC source connection terminals.

14. The electrical disconnect system as defined in claim 12 wherein all the circuit paths between said phase and neutral input terminals and said ground input terminal include components that block current when the voltage from said source of AC voltage is within the normal electric utility supply voltage range and said blocked current is less than both the steady-state and transient current limits permitted under the method for leakage current testing as specified by recognized electrical safety testing agencies to preclude electric shock hazard.

15. The electrical disconnect system as defined in claim 12 wherein said charge circuit of said capacitor includes a controlled switch in series with said capacitor and said input terminals that allows said capacitor to charge to said disconnect switch operating level only when said power frequency overvoltage reaches a level that is to open said disconnect switch.

16. The electrical disconnect system as defined in claim 15 wherein said controlled switch in the charge circuit of said capacitor includes load terminals in series therewith, a control terminal and connection thereof to said input terminals that keeps the load terminals non-conductive until said control terminal receives a given control voltage.

17. The electrical disconnect system as defined in claim 16 wherein said controlled switch is a transistor.

18. The electrical disconnect system as defined in claim 16 further including a threshold voltage conducting device in series with said control terminal so that said given control voltage is not applied until a power frequency overvoltage reaches a level that is to open said disconnect switch.

19. The electrical disconnect system as defined in claim 16 further including a threshold voltage triggered switch in series with said control terminal so that said given control voltage is not applied until a power frequency overvoltage reaches a level that is to open said disconnect switch.

20. The electrical disconnect system as defined in claim 16 wherein the circuit of said control terminal includes a low-pass filter that will not significantly reduce the level of said control voltage resulting from a power frequency overvoltage;

but will reduce said control voltage to a level less than that required to activate said controlled switch when a short duration transient voltage surge occurs at said input terminals, said short duration transient voltage surge being of the greatest magnitude in the environment for which the system is designed.