Patent GB-1383113-A (GB)
Title: Circuit arrangement for measuring electrical energy flowing in any one of two opposite directions
IPC: G01R21/133
Filed: 1972-06-12
Abstract: 1383113 Measuring energy SIEMENS AG 12 June 1972 [11 June 1971] 27410/72 Heading G1U [Also in Division G4] A circuit for measuring electrical energy flowing in each of two opposite directions along a conductive path, the input to the circuit being a voltage proportional in magnitude and direction to the electrical energy, has means for feeding the voltage via polarity reversing means to an integrator and threshold devices on the integrator output which reverse the input polarity as alternative positive and negative thresholds are reached and direct the pulse train produced to one of two counters. When the input polarity to the circuit changes due to a change in the direction of energy flow, the above circuit ceases to function and a second threshold circuit is activated to restore the action of the first circuit and to direct the pulse train to the other of the two counters. As shown, the input voltage and reversing means are represented by voltage + and -U o  and changeover switch S 1 , S 2  operated by solenoid S. This switch is connected to integrator J and the integrator output is connected to two threshold devices T 1 , T 2  operating at voltages U 1 , U 2  of opposite polarity and preferably equal. The outputs R and S of the threshold devices are connected to the two inputs of bi-stable M1 and one output of this is connected to AND gates N and hence counter ZW1 and ZW2 and also via exclusive OR gate A to solenoid S. Two other threshold devices T3, T4 operating at higher voltages U 3 , U 4  then T1, T2 respectively are connected via an OR gate to the switching input of bi-stable M2, the outputs of which are connected to AND gates N and one of them to gate A. Solenoids B1, B2 are also activated by actuation of respective triggers T3, T4 and supply a voltage of  U c  to the integrator input. In operation with inputs as shown which represents power flow in a first direction, bistable M2 is in the lower position and line m 1  is connected to counter ZW1. Switch S is in position S2 and applies - U o  to the integrator as shown in Fig.4. The integrator output U a  rises to U 1  when T1 operates switching M1 to give an output ml on lead L. This output passes a pulse to counter ZW1 and also actuates solenoid S via gate A. +U o  is then applied to the integrator and the output drops until U 2  is reached when T2 is actuated and the input again reversed. The output is thus a pulse train of repetition frequency proportional to U o . If at time t 2 , Fig.4, the input polarity changes due to a change in direction of power flow, the integrator output will fall due to the positive input and at time t 3  will reach U 2  operating threshold via T 2 , Ml will not switch and the voltage will continue to drop until the threshold U 4  of T 4  is reached. Bi-stable M2 will switch applying pulse m2 to operate S and to switch pulses m 1  when they restart to counter ZW2. The reversed input causes the circuit to operate as before but the pulses are now directed to the other counter, thus registering energy flow in the opposite direction. When there is no energy input, error voltages may cause the integrator output to rise. When threshold T 1  is actuated, operation of switch S has no effect on the error voltage and the rise continues. At threshold T 3  (voltage U 3 ) relay Bl is activated and a voltage +U c  is applied to the integrator input, reducing the integrator output voltage until it is below the "dropout voltage" of threshold device T3 when relay B1 becomes de-energized. The integrator output will then vary about voltage U 3  by the hystresis voltage of the threshold device T3 until an input is applied when the system reverts to normal operation.