US1985299A - Means for obtaining directional control on a current relay - Google Patents

Description

Dec. 25, 1934. J, J SAMSON 1,985,299

MEANS FOR OBTAINING DIRECTIONAL CONTROL ON A CURRENT RELAY Filed May 15, 1933 Patented Dec. 25, 1934 UNITED STATES PATENT OFFICE MEANS FOR OBTAINING DIRECTIONAL CONTROL ON A CURRENT RELAY 11 Claims.

This invention relates to electric systems, and more particularly to such systems, especially al ternating current systems, as are provided with means for protecting the same against reverse power flow.

Alternating current systems have heretofore been provided with means for opening the line circuit upon a reversal in the direction of power flow accompanied by a current flow exceeding a certain value. The mechanism for opening the line circuit is timed so that the greater the value of the current "flow when the direction of power flow is reversed, the smaller the time delay in the operation of the mechanism.

In a reverse power relay that 'is intended to have an inverse time current characteristic, it is essential that the timing shall commence immediately upon the reversal of power, and that, for a given current flow, the time delay should always be the same, depending upon the setting of the apparatus. These conditions are not always readily'obtainable. In one type of-relay of this kind with which I am familiar, there is provided a power directional element which closes one contact upon a reversal of power flow, and there is provided a current element which closes another contact if the line current exceeds a given amount for a time interval which varies inversely with the amount of current flow. When both of these contacts are closed, there is established a circuit for tripping a line circuit breaker. In such an arrangement, an incorrect opening of the line circuit may occur if there is a sudden momentary reversal of power flow immediately after the occurrence of an overload. When the overload occurs, the contacts of the over-current element are closed even though the direction of the power flow is such that the directional element contacts are open. Under such conditions, a momentary reversal of power flow may cause a closure of the directional element contacts before the contacts of the over-current element have had sufficient time to open. This brings about an immediate opening of the line circuit without timing, even though there may have been no appreciable overload at the instant of reversal of power flow.

In a system with which I am familiar, it has been proposed to overcome this difliculty by preventing operation of the over-current element until the directional element contacts are closed, this being accomplished by extending one of the circuits of the current element through contacts of the directional element. I have found that, although this does solve the problem of preventing incorrect opening of the line, it is quite unsatisfactory. This introduces another, and far more serious danger in that, by such an arrangement, the relay may fail to open when it should open, or its timing may become erratic. This is due to the fact that, under severe faults, the voltage of the line is low and, therefore, the directional contacts may close very lightly so that any film of oxide, or other foreign material, on the contacts may introduce an appreciable resistance in the circuit of the over-current element and thus delay, or even prevent, the operation of the over-current element. This, at a time when fast and positive relay action is required.

In accordance with my present invention, I propose to eliminate the possibility of incorrect opening. while, at the same time, maintaining the timing characteristics of the current element independent of the line voltage and assuring the operation of the directional element in proper time-current relation to the operation of the directional relay. I accomplish this result by providing an auxiliary relay which is energized instantly upon the operation of the directional element regardless of the pressure of contact of the directional contact, and, upon operation, establishes an operating circuit for the over-current element which then commences its timing operation. This auxiliary relay is energized from a source of power separate from the line, such as a storage battery, so that its rate of operation will not be affected regardless of the extent of drop in line potential brought about by the overload or fault condition.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

The single figure of the drawing is a circuit diagram illustrating my invention.

Reference may now be had more particularly to the drawing. In the drawing I have shown a portion of an alternating current line at 1, said portion being comiected through a circuit breaker 2 to an adjacent portion of the line 3. The line may be any type of alternating current line and may be supplied with power from either or both ends. By way of illustration, the section 1 may comprise a portion of a large power loop that is supplied with power at both ends, and furnishes power to a number of consumers along the loop.

My improved relay comprises a power directional element 5 controlling a pair of contacts 6, a Current element '7 controlling contacts 8, an

auxiliary relay 9 controlling the circuit of the current element 7, a trip circuit relay 10 and an operation indicator 11. The operation indicator may comprise an electromagnetic drop which, when momentarily energized, releases a drop signaling flag 12. The power directional element 5 and the current element 7 are of substantially similar constructions, well known in the art, comprising induction type relays. The relay 5 comprises'a metallic stamping of the shape shown, which constitutes the field struc ture. The directional element 5 comprises a standard induction type watthour meter, of which the current coils, indicated at 16 and 17, are wound on the two upper poles and connected in series. The potential coil 15 is on the main lower pole. The moving part of this element comprises a rotating copper disc 18 controlled by a light spring which closes the contacts 6 as nearly simultaneous with the reversal of power as possible.

The current element includes a main coil 20 provided with a number of taps which are con' trolled in any desired manner, as by a switch 21, so that any desired number of turns of the coil 20 may be connected in the circuit. The two auxiliary coils 16' and 1'7 are energized from the secondary of a torque compensator 23, the primary of which is fed inductively from the main coil 20 by a winding 24 located on the same pole as the main coil winding.

The moving member of the current element 7 comprises a thin aluminum disc 25 which is held against rotation by a spiral spring. The actual operation of the relay is simply that, when a certain amount of current is flowing in the coil 20, sufiicient torque is exerted on the disc to start it to rotate. The rotation of the disc is caused by the same action as that causing the rotation of the disc in any of the present day induction type instruments. When the disc has rotated through a given distance, it closes the contact 8. The speed of rotation of the disc is determined by the amount of current flowing through the winding 20 and, therefore, the time required for operating the contact 8 decreases as the magnitude of current flowing through the coil 20 increases.

The potential coil 15 of the power directional element 5 is energized from the secondary 28 of a potential transformer 29. The secondary of a current transformer 30 is connected in series with the current coils 16 and 17 of the element 5 and with the coil 20 of the current element '7, which coil is normally shunted out by the back contact of the normally deenergized relay 9.

The operation of myimproved device is as follows:

The directional element 5 is always responsive to the direction of power flowing in the line and will not close its contacts 6 unless the direction of power flow is reversed. An overload which is not accompanied by a reversal of direction of power flow is of no effect upon the element 7, since the coil 20 is short-circuited by the relay 9. Upon reversal of power flow, the directional element 5 immediately closes its contact 6, and thus establishes a circuit for the operating winding of the auxiliary relay 9, said circuit extending from the negative side of a 120-volt battery 30, through the operating winding of the relay 9, through the contact 6 and the operating winding of the relay 10, to a terminal 31 that is connected to the positive side of the battery. The operating windings of the relays 9 and 10 are thus connected in series. The relay 9 is a very high resistance relay and requires approximately onetwentieth of an ampere for operation. The relay 10 is a low resistance relay and requires about two and one-half amperes for operation. The current flow through this series circuit is limited by the high resistance of the relay 9 to such a value that the relay 9 operates, but the relay 10 does not operate. The operation of the relay 9 is substantially instantaneous, its resistance being so high that any reasonable amount of resistance that may be introduced at the contacts 6 can produce no appreciable effect in the operation of the relay 9. Also, the full battery voltage is available to breakdown any film of oxide that may have formed on the directional contacts 6. Upon operation, the relay 9 opens the short circuit around the coil 20 of the current element 7. If the overload of the line is, at this time, below the value for which the current element '7 is set, the element 7 will not'opei'ate, and after a period of time, whe'n the direction of power flowing in the line corrects itself, the power directional element 5 will open its contacts 6 to open the circuit for the auxiliary relay 9 which drops back to reestablish the normal condition of the relay. On the other hand, if the overload on the line exceeds the value for which the current element '7 was set, the'disc 25 commences to rotate and, after an interval of time, depending upon the magnitude of the overload and the setting of the switch 21, the

contacts 8 close. Upon closure of the contacts 8 there is established anopei'ating circuit for the winding of the relay 10, said circuit extending from thepositive side of the battery 30', through the terminal 31 and the winding of the relay 10,

through the contact 6 or the directional element -5, and the winding of the drop 11, thence through the contacts 8 and conductor 40, through the tripping winding of the circuit breaker 2, through front contacts 43 of the circuit breaker, if the circuit breaker happens to be closed, to the negative side of the battery. The operating winding of the relay 10 is now connected in series with the tripping winding of the circuit breaker. relay 10, upon operation, establishes a locking circuit for itself, by way of its contact 44, and

thus short circuits the winding 11. This does not afiect the operation of the drop since the signaland of the drop 11, said circuit extending from positive potential on the terminal 31, through the winding of the relay 10, the contact 44, to the tripping winding of the circuit breaker 2, thence by way of the closed contacts 43 to the negative side of the battery. The current flowing through this circuit is sufiicient to trip the breaker. This circuit is maintained until the circuit breaker trips and, at its contact 43, opens this circuit. This brings about a deenergization of the relay 10 which now drops back. The circuit breaker 2 is now open, thus protecting the line, and the drop 12 is now down to indicate that the circuit breaker has been opened. The drop 12 is located in front of a window in the casing of the protective mechanism, so that an operator, by noting the position of the drop, is apprised of the fact that the circuit breaker has been tripped.

The contacts that are connected by conductor 45 are, in turn, connected to a terminal 46, which terminal may be connected to signaling equip- The ment in any desired manner so that the signaling equipment will operate simultaneously with the operation of the circuit breaker 43, it being noted that the circuit to the terminal 46 corresponds to the circuit established by the contacts 8 and 44 to the conductor 40 that extends to the circuit breaker.

From the description above given, it is apparent that the amount of current flowing through the various windings of the current ele ment 7 is independent of the degree of contact established by the directional element 5 so that, even though poor contact is established at 6, the amount of current flowing through the windings 20 and l6-1'7' will be dependent solely upon the amount of current flowing through the line; hence the timing of the element 7 is not interfered with in the event that the voltage for operating the directional element 5 is materially reduced. The relay 9 is energized from a separate source of power to control the commencement of the energization of the current element 20. I believe this to be fundamentally new.

In compliance with the requirement of the patent statutes, I have herein shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise arrangement herein shown, the same being merely illustrative. What I consider new and desire to secure by Letters Patent is:

1. An alternating current system wherein there is provided a contact controlling power directional element and an inverse time overload current element and a line circuit breaker is arranged to be tripped by the joint action of the two elements, characterized in that there is pro vided a relay short circuiting a controlling portion of the inverse time overload current element and there is provided a source of potential controlling the relay in a circuit under control of the power directional element and of a magnitude sufficient to break down any film of impurities that may form on the contacts of said directional element.

2. An alternating current system wherein there is provided a contact controlling power direc tional element and an inverse time overload current element, means for delaying the timing of the overload current element until the directional element has operated, and a line circuit controlling device controlled by both elements, characterized in that the timing delaying means includes a source of potential which is of a magnitude sufficient to break down any film of impurities that may form on the contacts of the directional element.

3. An alternating current system wherein there is provided a power directional element and an inverse time overload current element, means for delaying the timing of the overload current element until the directional element has operated, and a line circuit controlling device controlled by both elements, characterized in that the timing delaying means includes means for completing the circuit of the overload current element independent of the pressure of engagement of the directional element contacts.

4. An alternating current system wherein there is provided a power directional element and an inverse time overload current element, means for delaying the timing of the overload current element until the directional element has operated,

and a line circuit controlling device controlled by both elements, characterized in that the timing delaying means includes a relay having contacts normally short circuiting an operating winding of the overload current element, and a source of potential which is substantially unaffected by variations in line voltage during fault conditions, said source of potential controlling said relay over a circuit controlled by the power directional element.

5. An alternating current system wherein a contact controlling reverse power element is effective responsive to a reversal of power flow to control an inverse time current element for controlling the line circuit, characterized in that there is provided means maintaining a substantially fixed voltage across the contacts of the reverse power element for rendering the timing of the circuit controlled thereby substantially independent of voltage variations during fault conditions.

6. In combination, an alternating current power directional element having an operating contact included in a high resistance circuit comprising a relay winding and a source of potential, an inverse time overhead current responsive element, and means controlled by the relay for controlling the overload current element.

7. In combination, a power directional element,

contacts controlled thereby, means maintaining a fixed voltage across the contacts, an inverse time over current element, and means controlled by the contacts for controlling the over current element.

8. In combination, a power directional element, contacts controlled thereby, means maintaining a fixed voltage across the contacts, an over current element, a relay short circuiting a controlling portion of the over current element, and an operating circuit for the relay, said circuit being controlled by the directional element contacts.

9. In combination, an alternating current power distribution system, a circuit breaker therein, and means for opening said breaker upon reversal of power flow in said system comprising a power directional element, contacts controlled thereby, means maintaining a fixed voltage across the contacts, an inverse time over-current element, means controlled by said contacts for controlling the over-current element, and means responsive to operation of said over-current element for tripping said breaker.

10, In combination, a power directional element, contacts controlled thereby, means maintaining a fixed voltage across the contacts, an inverse time over-current element, energizing means for said over-current element, means normally by-passing said energizing means, and means responsive to closure of said contacts for opening said by-passing means.

11. In combination, a power directional element, a fixed voltage circuit controlled thereby and including a set of normally open contacts, a high resistance relay in said circuit, an inverse time over-current element adapted to be actuated upon operation of said relay, a circuit breaker tripping circuit, a low resistance relay in series with said first relay, means controlled by said over-current element for by-passing said first relay to effect actuation of said second relay, and means responsive to actuation of said second relay for connecting said fixed voltage circuit to said tripping circuit.

JONAS J. SAMSON.

EERTIFECATE 0F CQRREQTEUNE Patent N0. 1,985,299. Eecember 25, 19 4.

WNAS .1. SAMSQN.

2a; arm? appears 111 um prmuzu' spaacificaiiw i.

Cami {ssh-22212 fine 3; i5; hereby certi'iis the ebiwe numbered reqa ring mire-mien as ialisws; Stage 3 se 26, siaim 6, far "overh 6 read mum; and mat me said Letters Patent shmiid e H be rem? with this mrrefitmn therein that the same may asniarm to the remrd @f the case in the Patent fiffice.

Signed and sealed this 5th day 0% March, A. 1935.

Leslie Frazer Acting iismmissianer of iatemts.

(Seal:

EERTIFICATE 0F CORRECTION.

Patent No. 1,985,299. December 25, 1934.

JONAS J. SAMSON.

it hereby certified that error appears no me prmteu specification of the the above numbered requiring correction as ioilows: Page 3, secood column, line the said Letters Patent should 26, claim 6, for "overhead" read. overload; and that he read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of March, A. l). 1935.

Leslie Frazer Acting Commissioner of iatents.

(Seal:

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