AU2013101333A4

AU2013101333A4 - Design Of The Triggering Circuit Of The Overvoltage Protection

Info

Publication number: AU2013101333A4
Application number: AU2013101333A
Authority: AU
Inventors: Jaromir Suchy
Original assignee: Saltek sro
Current assignee: Saltek sro
Priority date: 2012-08-28
Filing date: 2013-10-01
Publication date: 2014-01-09
Anticipated expiration: 2021-08-28
Also published as: DE202013103823U1; ZA201306018B; SK6943Y1; SI24191A2; ITAN20130073U1; SK500882013U1; CZ25171U1

Abstract

-9 THE The design of the triggering circuit 1 of the overvoltage protection, connected via three poles 4 to the spark gap of the overvoltage protection, provided with the first input terminal 2 and 5 the second main terminal 3, whose principle consists that an auxiliary electrode 7 of the spark gap 4 is connected in series to the first varistor 8 and one end of the secondary winding 14 of the transformer 13, the other end of which is connected to the second main electrode 6 of the spark gap 4and the second input terminal 3, whereas one end of the primary winding 1 of the transformer 13 is connected in series to the gas discharge tube 10, the second varistor 9, 10 resistor 11 and capacitor 12, connected to the other end of the primary winding 15 of the transformer 13, connected to the second input terminal 3, whereas the junction connecting the second varistor 9 to the resistor 11 is interconnected with the junction, connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4. The advantage of such a design of the triggering circuit 1 of overvoltage protection resides in 15 the thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9, is either connected in series to the second varistor 9, or connected to the link of the junction connecting the second varistor 9 to the resistor 11 and the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4, or that the thermo sensitive disconnector 17 is connected between the primary winding 15 of the transformer 13 20 and the gas discharge tube 10.

Description

EDITORIAL NOTE 2013101333 The last page of the description numbered 4 is a clerical error and should be there.

Design of the triggering circuit of the overvoltage protection Technological background 5 This invention relates to the design of the triggering circuit of the overvoltage protection, representing electrical protection circuits designed to reduce overvoltage in a protected distribution system. The overvoltage protection comprises the spark gap of the overvoltage protection provided with the first input terminal, the second input terminal, interconnected in three poles with the triggering circuit of the overvoltage protection. 10 Current state of technology The known technical solutions of triggering circuit designs of overvoltage protection devices deal with the excitation of the transformer primary winding directly by activating a 15 gas discharge tube with an overvoltage impulse. This design is simple, however, its correct functioning depends on the overvoltage pulse rise and so, in unfavourable circumstances, that is, if the rise of the pulse is low, i.e. the ratio of the voltage derivation to the time derivation is low, the auxiliary electrode of the spark gap will not activate and the discharge between the first main electrode and the second main electrode of the spark gap will not spark, which is 20 the reason why the concept of overvoltage protection is not functional. This shortcoming is partially resolved by other used designs of the triggering circuit of overvoltage protection comprising a capacitive divider and a gas discharge tube. An example of a more complicated design with a capacitive divider is document GB1076679 "Improvements in Triggered Spark Gap Type Surge Arrestors for D.C. Circuits"; a more 25 simplified design is shown in document US6111740 "Overvoltage protection system and overvoltage protection element for an overvoltage protection system". The disadvantage of these designs is the oscillation character of the current flowing through the triggering circuit of the overvoltage protection. With the oscillation current flowing through the secondary winding of the transformer going through zero, the discharge can extinguish between one of 30 the first main electrode or the second main electrode and the auxiliary electrode of the spark gap; whereas in such case the discharge between the first main electrode and the second main electrode of the spark gap will not be activated, which results in the absence of the protection function of the overvoltage protection. Instead of the capacitive divider, a divider with semi- -2 conductor voltage limiting components is also used, e.g. in document US4683514 "Surge voltage protective circuit arrangements". Another known design of the triggering circuit of overvoltage protection, shown in document FR2902579 "Electrical installation protection device i.e. surge suppressor, has a 5 triggering unit passing spark gaps from the blocking state, in which gaps oppose the current circulation, to the passing state, in which gaps permit fault current to flow in branches", or the one shown in document US2003/0007303 "Pressure-resistant encapsulated air-gap arrangement for the draining off of damaging perturbances due to overvoltages", deal with the above-mentioned drawbacks by using a combined divider with a varistor and capacitor. This 10 design of the triggering circuit of overvoltage protection eliminates in some respect the disadvantages of the previous designs, however, the oscillation character of the current flowing through the triggering circuit of the overvoltage protection still remains, and consequently the problem with possible discharge extinguishing between the first main electrode and the second main electrode of the spark gap, which results in the absence of the 15 protective function of the overvoltage protection. Basis of the invention The aforesaid disadvantages are eliminated to a large extent by the design of the 20 triggering circuit of the overvoltage protection, connected in three poles to the spark gap of the overvoltage protection, provided with the first input terminal and the second main terminal, whose principle consists in the case where an auxiliary electrode of the spark gap is connected in series to the first varistor and one end of the secondary winding of the transformer, the other end of which is connected to the second main electrode of the spark gap 25 and the second input terminal, whereas one end of the primary winding of the transformer is connected in series to the gas discharge tube, the second varistor, resistor and capacitor, connected to the other end of the primary winding of the transformer, connected to the second input terminal, whereas the junction connecting the second varistor to the resistor is interconnected with the junction, connecting the first input terminal to the first main electrode 30 of the spark gap. The overvoltage protection comprises a spark gap equipped with the first main electrode, the second main electrode, and one auxiliary electrode in order to make the breakdown between the first main electrode and the second main electrode easier, for which the design of the triggering circuit of the overvoltage protection is specified.

-3 The advantages of such a design of the triggering circuit of overvoltage protection offer better triggering ability due to the functioning part of the design of the triggering circuit of the overvoltage protection, located on the primary side of the transformer. To ensure the design of the overvoltage protection triggering circuit works safely, it is 5 advantageous that the thermo-sensitive disconnector coupled with the thermal coupling to the second varistor, is either connected in series to the second varistor, or connected to the link of the junction connecting the second varistor to the resistor and the junction connecting the first input terminal to the first main electrode of the spark gap, or that the thermo-sensitive disconnector is connected between the primary winding of the transformer and the gas 10 discharge tube. The mentioned advantageous design of the triggering circuit of the overvoltage protection, extended with a thermo-sensitive disconnector, enables disconnection of the triggering circuit of the overvoltage protection from the protected distribution system in the event of thermal overloading and impermissible heating or overheating of the second varistor, 15 and it prevents it being damaged or subsequent damage that could arise as a result of damage to the whole overvoltage protection. Drawing explanation 20 The invention will be more closely explained by using drawings, in which Fig. 1 shows the block diagram of the spark gap of the overvoltage protection, provided with the first input terminal and the second main terminal, connected in three poles to the triggering circuit. Fig. 2 shows the principal diagram of the spark gap of the overvoltage protection and 25 triggering circuit. Fig. 3 shows the principal diagram of the spark gap of the overvoltage protection and triggering circuit equipped with a thermo-sensitive disconnector which is coupled with the thermal coupling to the second varistor and, at the same time, connected between the second varistor and the junction connecting the first input terminal to the resistor. 30 Fig. 4 shows the principal diagram of the spark gap of the overvoltage protection and the triggering circuit equipped with a thermo-sensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected between the gas discharge tube and the second varistor.

-4 Fig. 5 shows the principal diagram of the spark gap of the overvoltage protection and triggering circuit equipped with a thermo-sensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected to the link between the junction connecting the second varistor to the resistor and the junction connecting the first 5 input terminal to the first main electrode of the spark gap. Fig. 6 shows the principal diagram of the spark gap of the overvoltage protection and the triggering circuit equipped with a thermo-sensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected between the primary winding of the transformer and the gas discharge tube. 10 -5 Realization of the invention - examples The overvoltage protection subject to Fig. 1 comprises a spark gap 4 of the overvoltage protection provided with the first input terminal 2 and the second input terminal 5 3 connected in three poles to a triggering circuit I of the overvoltage protection. The basic design of the triggering circuit 1 of the overvoltage protection according to Fig. 2 comprises an auxiliary electrode 7 of the spark gap 4 which is connected in series to the first varistor 8 and one end of the secondary winding 4 of the transformer 13, the other end of which is connected to the second main electrode 6 of the spark gap 4 and to the second 10 input terminal 3, whereas one end of the primary winding 15 of the transformer 13 is connected in series to a gas discharge tube 10, the second varistor 9, resistor 11 and capacitor 12, connected to the other end of the primary winding 5 of the transformer 13, connected to the second input terminal 3, whereas the junction connecting the second varistor 9 to the resistor 11 is interconnected with the junction connecting the first input terminal 2 to the first 15 main electrode 5 of the spark gap 4. The resistance of the resistor 11 is at least double that of the second root of the ratio of inductance of the primary winding 15 of the transformer 13 and capacitor 12 capacity. The advantageous windings of the triggering circuit 1 of the overvoltage protection are equipped with a thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the 20 second varistor 9. In its simplest embodiment, the thermo-sensitive disconnector 17 can be executed using a thermal fuse. The advantageous design of the triggering circuit I of the overvoltage protection subject to Fig. 3 is equipped with a thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, interconnected between the second 25 varistor 9 and the junction connecting the first input terminal 2 to the resistor 11. The advantageous design of the triggering circuit 1 of the overvoltage protection subject to Fig. 4 is equipped with a thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, interconnected between the gas discharge tube 10 and the second varistor 9. 30 The advantageous design of the triggering circuit 1 of the overvoltage protection subject to Fig. 5 is equipped with a thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, connected to the link between the junction connecting the second varistor 9 to the resistor 11 and the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4.

-6 The advantageous design of the triggering circuit 1 of the overvoltage protection subject to Fig. 6 is equipped with a thermo-sensitive disconnector 17 thermally coupled 16 to the second varistor 9 and, at the same time, interconnected between the primary winding 1 of the transformer 13 and the gas discharge tube 10. 5 The basic design of the triggering circuit 1 of the overvoltage protection subject to Fig. 2 is based on operating voltage of the protected distribution system between the first input terminal 2 and the second input terminal 3 in the absence of overvoltage, which is insufficient to spark the gas discharge tube 10, connected to the first input terminal 2 through the second varistor 9 and to the second input terminal 3 through the primary winding 15 of the 10 transformer 13. With the occurrence of impulse overvoltage between the first input terminal 2 and the second input terminal 3, the gas discharge tube 10 will ignite, whereas the second varistor 9 will show a deep drop in its resistance and the current impulse flowing through the primary winding 15 of the transformer 13 will induce high voltage in its secondary winding 14, which is then led through the first varistor 8 to the auxiliary electrode 7, and then the 15 discharge will spark between the auxiliary electrode 7 and the first main electrode 5 or the second main electrode 6 of the spark gap 4. The first varistor 8 maintains the discharge by showing a steep drop in its resistance. Consequently, as a result of ionisation of the space between the first main electrode 5 and the second main electrode 6 of the spark gap 4, the discharge will spark between the first main electrode 5 and the second main electrode 6 of the 20 spark gap 4. Due to the voltage drop between the first main electrode 5 and the second main electrode 6 of the spark gap 4 the current flowing through the auxiliary electrode 7 will drop, the first varistor 8 will steeply increase its resistance, as a result of which it will get into its initial condition. The discharge current from the charged capacitor 12 contributes to the increase in the initial rise of the current impulse through the primary winding 15 of the 25 transformer 13, and consequently the induced voltage in its secondary winding 14 will increase, which will improve the reliability of the activating or ionisation effect of the auxiliary electrode 7. The capacitor 12 charged through the resistor II integrates short overvoltage impulses with its capacity between the first input terminal 2 and the second input terminal 3, which would be insufficient to spark the gas discharge tube 10 and consequently, 30 the discharge spark between the first main electrode 5 and the second main electrode 6 of the spark gap 4 and so it ensures that the protection functioning will be maintained even in case a sequence of shorter overvoltage impulses occur. The resistor 11 inhibits the oscillation character of the current flowing through the triggering circuit 1 of the overvoltage protection, resulting from the existence of the resonance circuit represented by the inductivity of the primary winding 15 of the transformer 13 and capacitor 12 capacity. The advantageous embodiment of the design triggering circuit 1 of the overvoltage protection design subject to Figs. 3 to 6 are complemented with a thermo-sensitive disconnector 17, which enables disconnection of the triggering circuit 1 of the overvoltage protection from a protected 5 distribution system in the event of thermal overloading and impermissible heating or overheating of the second varistor 9. An equivalent function of the design of the triggering circuit I of the overvoltage protection occurs in serial layout of the circuit elements of the second varistor 9 and the gas discharge tube 10, and/or the resistor 11 and capacitor 12, in reverse order, than is shown in 10 Figs. 2 to 6. Application in industry The design of the triggering circuit of the overvoltage protection subject to this 15 invention can be used in all applications where the distribution systems are at risk of overvoltage. Unlike the known designs, this invention shows better triggering ability and thanks to the provided thermo-sensitive disconnector, further failures resulting from damage to the whole overvoltage protection can be prevented.

List of symbols 1 triggering circuit 2 the first input terminal 3 the second input terminal 4 spark gap 5 the first main electrode 6 the second main electrode 7 auxiliary electrode 8 the first varistor 9 the second varistor 10 gas discharge tube 11 resistor 12 capacitor 13 transformer 14 secondary winding 15 primary winding 16 thermal coupling 17 thermo-sensitive disconnector

Claims

1. The design of the triggering circuit I of the overvoltage protection connected via three 5 poles to the spark gap 4 of the overvoltage protection, equipped with the first input terminal 2 and the second input terminal 3, is distinguished by the auxiliary electrode 7 of the spark gap 4, which is connected in series to the first varistor 8 and one end of the secondary winding 14 of the transformer 13, whose other end is connected to the second main electrode 6 of the spark gap 4 and to the second input terminal 3, whereas one end of 10 the primary winding 15 of the transformer 13 is connected in series to the gas discharge tube 10, the second varistor 9, resistor 11 and capacitor 12, connected to the other end of the primary winding 15 of the transformer 13 connected to the second input terminal 3 whereas the junction connecting the second varistor 9 to the resistor 11 is interconnected with the junction, connecting the first input terminal 2 to the first main electrode 5 of the 15 spark gap 4.

2. The design of the triggering circuit I of the overvoltage protection subject to claim 1, is distinguished a thermo-sensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9, which is either connected in series to the second varistor 9, or is connected to the link between the junction connecting the second varistor 9 to the resistor 20 11 and the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4, or the thermo-sensitive disconnector 17 is connected between the primary winding 15 of the transformer 13 and the gas discharge tube 10. 25 30