US1713698A - Relay system - Google Patents

Description

y 21, 1929- w. e. HICKLING 1,713,698

RELAY SYSTEM Filed Oct. 15, 1923 3 Sheets-Sheet 1 WITNESSES: INVENTOR y 21, 1929- w. e. HICKLING 1,713,69

RELAY SYSTEM Filed Oct. 15, 1923 6 Sheets-Sheet 9 WITNESSES: INVENTOR y 1, 1929. w. cs. HICKLING ,6

RELAY SYSTEM Filed Oct. 15, 1925 3 Sheets-Sheet 3 A B C 0 E F 6 H J K 56 FyZ 37 A a c 0 E F a H-J K58 P an 60 70 so .5}; 40 do 20 m Vo/izzge- WITNESSES: INVENTOR ag/ 44 BY @414 ATTORNEY gardless of the Patented May 21, 1929.

UNITED STATES WILLIAM G. HICKLING, OF JOHNSTOWN, PENNSYLVANIA.

RELAY sxs'rrm.

Application filed October 15, 19523. Serial No. 668,503.

My invention relates to relay systems and particularly to relay protective devices for power transmission systems.

One object of my invention is to provide a relay system that shall eflectively protect a power transmitting and distributing system by, selectively isolating a faulty section of the system.

Another object of my invention is to provide a relay system, of the above-indicated character, that shall automatically adjust its time of operation according to the distance of the particular relay from the location-of a faulty condition in the system, re-

generating capacity of the system.

Another object of my invention is to provide a system, of the above-indicated character, that shall be operative to disconnect a section of the system only when the condition of low voltage thereon is caused by an execssive current traversing that section.

In practicing my invention, I provide a plurality of under voltage relays having an inverse-time-element characteristic that are respectively energized in accordance with the voltage of the several conductors of the sys tem.

In order to preclude the disconnection of any section of the system upon failure of voltage for any reason other than abnormal conditions, such as caused by short circuits, I

.may provide in some installations a current relay or a reverse-energy relay that is energized to close its contact members when current traverses the associated section. The contact switch of the auxiliary relay cooperates with the cont-act switch of the voltage relay, to control the circuit of the trip coil of the associated circuit interrupter.

However the provision of the auxiliary relay is not essential in all cases and, where it is used, the time of closing the tripping circuit is that of the operation of the voltage relay only.

When an abnormal condition occurs at any point of the system, a potential gradient is established between that point and the source or sources of energy, and, since the voltage relays at different points of the system are energized in accordance with the value of the potential gradient at that point of the system, the relays that are nearest to the locaion of the faulty condition will be energized to the least degree. Since the voltage relays will adjusted to permit the closing of their contact members when the relays are energized at, or below, a predetermined minimum value, such as, for example, 40% of normal operating voltage, the contact members of the voltage relays nearest the location of the fault will close first. Under such conditions, the contact members of the current relay, if

employed, will also be closed and, if the curnearest the fault will be actuated, irrespective of the generator capacity connected to the system. It is becoming common practice to interconnect generating stations at certain times in large distribution systems and the generator capacity varies therefore over a wide range. The short-circuit current is determined by the generator capacity and accordingly may vary 1000% or more. It has been found that impedance relays having a current operating element and a voltage restraining element must be readjusted when the generator capacity is altered to such a great extent. If the relays are not readjusted, the excessive short-circuit current determines the operating time ofthe relays, the voltage restraining element being ineffective, and selective operation is not obtained. The present invention overcomes this difficulty, since the time element of the voltage relay is independent of the generator capacity.

Figuresl and 2 of the accompanying drawings are diagrammatic views of portions of ungrounded neutral electrical systems including relay. protective systems embodying my invention;

Figs. 3 and 4 are diagrammatic views of grounded neutral power systems provided with relay systems similar to those illustrated in Figs. 1 and 2;

Fig. 5 is a schematic view ofan operating system;

Figs. 6 and 7 are views of the system that is Fig. '8 is a curve illustrating the inversetime-element characteristic of the voltage resection by a protective relay system to disconnect the faulty section from the remainder of the system.

The protective relay system comprises a polyphase directive relay 3, a current relay 4 and three potential relays 5, 6 and 7 having inverse-time-element characteristics. The directive relay 3 has three current windings 14, and three potential windings 15. Three current transformers 8, 9 and 10 are connected in the circuit 1 and are provided to energize the current windings 14 of the directive relay 3 and also of thewinding of the current relay 4. Two potential transformers 12 and 13 are provided to energize the potential Windings 15 of the directlve relay 3 and also the wlndings 16 of the potential relays 5, 6 and 7 in accordancewith the voltage of the circuit 1.

Fig. 2 illustratesan arrangement similar to that in Fig. 1, except that the voltage elements 5, 6-and 7 and the directive elements 3 are combined in single-phase relays. The relay of this type comprises a directive element which closes its contact members when energy flows in a predetermined direction and a potential element which normally maintains its contact member open when energized to, or beyond, a predetermined degree, but,

permits the contact member to close when energized to a lesser degree.

Standard reverse-phase relays of the induction type may also be employed to combine the directive element and the current element in a manner similar to the combination of the directive and voltage elements illustrated in Fig. 2. With the latter arrangement, the

potential relays would beseverally connected and energized, as illustrated in Fig. 1, the

operation of the different elements still remaining the same as explained in connection with Fig.1.

In Fig; 3 is illustrated a section 20 of a sylslar to that illustrated in Fig. 1, with the exception that additional potential transformers 21, 22, and 23 are provided to energize the windings 16 of the potential relays 5, 6 and 7 in accordance with the voltage of the several phase conductors.

Figure 4 illustrates a system similar to that shown in Fig. 3 with the exception that singlephase relays are employed 1n which the directive element and the voltage element are combined, as illustrated in Fig. 2.

In Fig. 5 is illustrated a power system, in

which two generating stations 30 and 31 are provided to supply energy to the system which contains a plurality of sections each of which has two interrupters AB, GD, J-K, to isolate any one of the sections.

Under certain conditions, when the load demand is large, both stations will be operating and, if load conditions are normal, the potential gradient of. the normal operating voltage may be illustrated by the voltage line 32, as illustrated in Fig. 6 the ordinates of this line representing potential. Upon the occurrence of a short circuit or other abnormal condition at a point intermediate the stations, a potential gradient will be established from this point to both generating stations that may be illustrated by the voltage line 33.

Under the conditions last considered, causing the-drop in voltage in the system to correspond to'the voltage line 33, the voltage relays associated with the circuit interrupters 34 and 35 will close their contact members.

and disconnect the faulty section from the,

system to ermit the remainder of the system to contmue operating.

In Fig. 7 is illustrated the conditions arising when the load demand is within the capacity of station 30 alone and station 31 is shut down. Under normal conditions, the operating Volta e may be indicated by the line 36. Upon t e occurrence of an abnormal condition at the point P, beyond the station 31, a voltage gradient is established between that point and the station 30, and the voltage of. the system may be illustrated by the line 37. Under such conditions, the contact members of the directive, current and voltage relays, or elements, will be closed to complete the circuit of the trip coil associated with the interrupter 38, whereupon the interrupter will be opened to disconnect the faulty section from the system and the remainder of the system will continue in normal operation.

From a study of the power system that is considered here, it will be understood that it would be dilficult to provide protection for the system merely by means of overload relays having different settings, since the time and current setting of the different relays while one station would be operating would be dif ferent from that required when both stations were operating. By means of the present sysmatically adjust their time of operation so that the relays nearest the location of the fault will automatically reduce their time of.

operation and operate before the relays more remotely disposed.

' Since it is possible, though hardly probable, that the voltage of the system may be entirely removed for a short time, as by reason of the complete shut-down of station 30 while it alone is operating, the current relay is pro lays that are available, whereby a different time of operation may be procured for dif- 1ferent voltages by adjustment within the re- Although I have shown the application of several devices to a particular system in accordance withmy invention, various changes and modifications will be obvious to those skilled in the art, which will not depart from my invention and will be Within the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. Ina power system comprising a plurality of circuit sections provided with circuit interrupters therebetween embodying a trip coil, two switching devices connected in series circuit relation to control the circuit of the trip coil, means responsive to mere presence of the circuit current and independent of the magnitude thereof for actuating one switching device, and functionally independent means for actuating the other switching device when the voltage of the system at the interrupter is less than a predetermined value and for exclusively controlling the timing of the circuit interrupter actuation. S

2. In a three phase system havin a generator connected thereto, the com ination with a circuit-interrupter therefor, of a current transformer for each phase, potential transformers, a current element having no current value adjustments to correspond to varying values of the connected generator capacity and being energized from the current transformers, a switch controlled thereby, a voltage element for each phase functionally independent of the prior effectiveness of the current element and energized from the po-" tential transformers, a switch controlled by the voltage element to cooperate with and connected in series circuit relation with the other switch to control the circuit interrupter when the phase potential decreases below a predetermined value after a predetermined time and such condition is attended by the presence of a current condition independent of the magnitude thereof causing the current element to operate its switch.

3. Protective apparatus for a line to be protected in an electric system, including a circuit interrupter controlled by a trip coil, a plurality of contact switching devices connected in series circuit relation for controlling the trip coil, means including a Watt relay for actuating one of the contact switching devices when energy traverses the interrupter in a predetermined direction independent of the magnitude of the energy, and a relay functionally independent in. its own operation from the effectiveness of the lastnamed means for actuating another of the contact switching devices and having a timeelement for exclusively controlling the time delay actuation of the interrupter.

4. Protective apparatus for a line to be protected in an electric system having a generator connected to the system, including a circuit interrupter controlled by a trip coil,

a plurality of contact switching devices con-' trolled by a plurality of relays and connected in series circuit relation for controlling the a trip coil, the plurality of relays including a relay functionally independent in its own operation from the effectiveness of the associated relays for actuating one of the contact switching devices when the voltage of the system at the interrupter is less than a predetermined value and having a time-element for exclusively controlling the time-delay actuation of the interrupter, a relay for actuating another of the contact switching devices when energy traverses the interrupter in a predetermined direction, and a relay having no current value adjustments to correspond to variations of the connected generator capacity for actuating still another of the contact switching devices when any value of current independent of magnitude, traverses the interrupter.

5. Protective relay, apparatus for an electric power system having a generator connected thereto and being severally sectioned into lines to be protected, including a circuit interrupter controlled by a release or trip coil circuit for each end of each line to be pro tected, a set of relays associated with each circuit interrupter, including a voltage relayenergized from the line in accordance with the voltage at the point of the line to which it is connected and having a time element substantially inversely proportional to the voltage drop at that point and having a contact switching device controlled by the voltage relay, a directive rela having a contact switching device and being responsive to the direction of power traversing the line, and a current relay having a contact switching device responsive to mere presence of line current and independent of the magnitude thereof and having no current value adjustments to correspond to variations of the connected generator capacity, the contact switching devices of theset of relays named being connected in series circuit relation with each other and with the circuit interrupter trip coil circuit, and the set of relays being characteriz'ed by the fact that the operation of the voltage relay is functionally free and independent'of the operation and prior effectiveness of the associated relay, and that the circuit interrupter tripping timing is con-- trolledsolely'b the voltage relay alone and independent 0 the magnitude of the line current. i

6. Protective apparatus for a three-phase line to be protected in an electric system comprising, a circuit interrupter having a trip coil, three current transformers, one connected to each of the conductors of the line to be protected and all connected in star, po tential transformersconnected to the line for obtaining voltages correspondin to the phase voltages severally, three functionally independent voltage relays each having a windlng energized by a different phase voltage and all having a'set of independent switch 1,7is,eee

contacts connected in parallel circuit relation with each other, three watt relays having tacts, and a single current relay having a single windin g connected to the current transformers and having'a set of switch contacts connected in series circuit relation with the named sets of contact switches and the trip coil of the circuit interrupter.

7. In an electric system, the combination with a transmission circuit and a circuit interrupter therefor, of a relay responsive to the direction of current traversing the circuit, a second relay responsive to the voltage of said circuit at said interrupter and having a time-delay in accordance with the magnitude thereof, said relays cooperating to actuate said interrupter only upon the occurrence of a fault and with a time-delay determined exclusivcly by said second relay independent of the magnitude of the current traversing said system.

In testimony whereof, I'have hereunto subscribed my name this-8th day of October,

WILLIAM G. HIUKLING.

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