Patent GB-583567-A (GB)
Title: Arrangement for selective protection of electric lines
IPC: H02H7/26
Filed: 1944-11-02
Abstract: 583,567. Protective cut-out systems. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Nov. 2, 1944, No. 21437. Convention date, Nov. 9, 1943. [Class 38 (v)] In a protection arrangement for power lines divided in sections, each section has a distance protection device at its ends, which operates with a quick release reach longer than the length of the section, Fig. 1a. Fig. 5 shows the equipment at one end of a section. Release of the breakers of the faulty section only is achieved by the blocking of the device at the farther end of the adjacent section, whose quick release reach extends into the faulty section, by means of an auxiliary current transmitted over a pilot line or power line itself, as shown. When a fault occurs, such as in Fig. 2, in the region Í2 of Fig. 1a, on a line fed from both ends, the distance protection devices Ah, Bv, Cv give release impulses and the starting members (not shown) thereof close contacts 3, and open contacts 32 to interrupt the transmission of auxiliary current from all the generators 6. In the opposite stations the auxiliary current receivers 5 close contacts 51, 5<2> and open 5,. Thus the transmission of auxiliary current from Ah, Bv and Cv is blocked and the breakers Ah, Bv of the faulty section are tripped when the directional member (not shown) closes its contact 4,. Release of Cv is blocked by the auxiliary current transmitted by closing of directional contact 42 of Bh. A time-relay 8 operated by the contact 52 closes contact 8, after a predetermined time sufficient to clear the fault, to re-establish the mutual transmission of auxiliary currents. Similar protection also obtains for a line fed from one end. In the case of circuit-breakers provided with rapid reclosing mechanism, the breaker whose quick release reach extends into the faulty section has that reach changed from long to short after the first release impulse, thereby ensuring that only the breakers of the faulty section are released on the reception of a second and definite release impulse. In Fig. 6, a fault occurring on the auxiliary current system causes a relay to close contact 16, and energise a blocking relay 11 which, through contacts 111, 112, disconnects that system from the protection device and allows the latter to function in its characteristic manner in the event of a further fault on the power line. Contact 113 interrupts the transmission of.auxiliary current and after a time lag, the relay at the other end of the section operates to block that end also. A relay 12 energised by contact 115 closes contact 12, to enable the use of the system for other purposes (e.g. telephony). Restarting of the auxiliary currents takes place at both ends simultaneously by means of a pushbutton 13 at each end energising a relay 14. Contact 142 interrupts the transmission of auxiliary current and 14, tries to break the holding of relay 11, but will not succeed until the far-end button 13 is also pressed to open contact 52, after which relays 11, 12 are deenergised and normal coupling of the auxiliary current arrangement re-established.