DE608441C - Protection circuit for electrical systems - Google Patents

Description

GERMAN EMPIRE

ISSUED ON JANUARY 25, 1935

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21c GROUP 68 so

General Electricity Society in Berlin *)

Protection circuit for electrical systems

Addition to patent 596

Patented in the German Empire from June 9, 1932 The main patent started on May 16, 1930.

The subject of patent 596 010 is a protective device for electrical systems, which in the case of a double earth fault, both of which are earth faults in different branches of the line only switches off one of the two grounded branches. For this purpose there are several in each station Phase monitoring relays in the event of a double earth fault, all but one, the one in all Stations in the same phase is blocked in such a way that they are independent of whether they are from a short-circuit magnitude are excited, do not trigger the associated station can. If z. B. with the one shown in Fig. 1

1-5, the double earth fault applies to phase U in branch A , phase W in branch B and the protective device is set so that only the relays of phase U are triggered in all stations

ao only the protective device in station A is activated.

This means that if the protective device fails in this station, there is a double earth fault is switched off in the other station, the blocking is according to the invention the relay only carried out for a certain period of time. The time during which the trip is after the actuation of the relay contacts is blocked, if monitoring relays are used with an impedance-dependent time characteristic, appropriately chosen somewhat larger than the longest Switch-off time of the time lapse relay, which occurs if the error is still within the to monitored part of the system is located. There is generally a 2 to 4 second delay get along. This ensures that if one protective device fails, the other within the one to be monitored Plant part lying is actuated before the error is elsewhere and therefore not can be switched off more selectively.

In Fig. 2 an embodiment for a monitoring device with only two current-dependent monitoring relays uw in the phases UW is shown. The contacts Ci _{1 of} the relay u are directly in series with the trip coil 0 and the local battery, the contacts a ₃ as in the arrangement of the main patent via contacts g of the relay c, which is actuated by the earth fault relay when the voltage drops between the phases UW b via a blocking device d

*) The patent seeker stated as the inventor:

Dr. Rolf Wider de in Vinderen, Oslo.

B. when a double earth fault occurs between "" the "phases UW , the relay w is not made completely ineffective, but a timing relay ζ is placed in the tripping circuit of its contacts a ₃ via the changeover contacts m , which after a certain set time actuates its contacts p and thus closes the excitation circuit of the trip coil ο via contacts m and a _3.

ίο Fig. 3 shows a three-phase protection with three relays u υ w in all three phases. The actuation contacts of relay Ci ₁ are again switched directly into the excitation circuit of the trip coil ο; the contacts a _{s of} the relay w as in the embodiment 1 via the contacts g and m of the relay c. The contacts A ₂ of the third relay are ν now via the normally closed contacts f of the earth-fault also b in the current circuit of the trip coil 0. However, η on the changeover timing relay is b in response of the earth-fault switched ζ that the exciter circuit of the coil 0 after a certain time on the contacts p closes.

If a double earth fault occurs between the phases UW , the contacts O ₁ and a _{s are} actuated. The station in which the fault current flows in phase U should «! trigger. If this does not happen, then in the other station, in which the fault current flows in phase W , the excitation circuit of the trip coil is closed via the contacts a ₃ and m and the contacts actuated after a certain time. In the event of a double earth fault between UV , relay U actuates first, relay ν with a delay, actuates the trip circuit; In the event of a double earth fault between VW, relay w first and, if it fails, relay v.

Claims (5)

Patent claims: i. Protective circuit for electrical systems according to patent 596010, characterized in that the monitoring relays (a _v a ₂ , a _s ) are only blocked for a limited time. 2. Protection circuit according to claim 1 with only two monitoring relays for a three-phase line, in which in series with the contacts of a monitoring relay, the contacts of a relay device responding to a voltage drop between the phases equipped with monitoring relays and simultaneous earth fault are, characterized in that the Contacts of this relay device are designed as changeover contacts (g, m) in such a way that a timer (z) is switched on when the relay is actuated, the contacts (p) of which only close the excitation circuit of the trip coil (0) after a set time has elapsed (Fig. 2). 3. Protection circuit according to claim 1 with monitoring relay in all three phases of a three-phase line, characterized in that the timing relay (z) when the earth fault relay (b) responds in the operating circuit of the monitoring relay (v) of a phase (F) is switched and at the same time Response of a relay (c) dependent on the voltage drop between the two other phases (U, W) in the control circuit of the monitoring relay (w) of one (W) of these phases (Fig. 3). 4. Protection circuit according to claim 1 to 3, characterized in that when used of monitoring relays with impedance-dependent time characteristics the time during which the triggering is blocked after actuation of the relay contacts is somewhat larger is selected as the longest switch-off time of the timing relay that occurs when the The error is still within the part of the system to be monitored. 5. Protection circuit according to claim 1 to 4, characterized in that the time during which the triggering is blocked after actuation of the relay contacts is about 2 to 4 seconds. 1 sheet of drawings