JPS60200175A - Multi-phase electronic type electric watthour meter - Google Patents

Abstract

PURPOSE:To eliminate the mutual balance error between powers, by interchanging the connection relation of a resistor and a multiplier at every definite period and bringing a current value classified by phases flowed into an imaginary earth point to the average value of the current obtained by converting the output voltage of a multiplier classified by phases by a resistor. CONSTITUTION:Because analogue switches 10, 11 are turned ON and analogue switches 9, 12 are turned OFF for a definite period when the output Q of T-type FF8 is a low level and the output Q thereof is a high level, the output voltage ep1 of a multiplier circuit 4 is applied to a resistor R2 and the output voltage ep2 of a multiplier circuit 5 is applied to a resistor R1 and both voltages are converted to currents to receive current synthesis at the imaginary earth point of a current-frequency converter circuit 6. Because the resistors R1, R2 connected to multipliers 4, 5 are interchanged at every definite period and interchanging is repeated, the output voltage ep1 of the multiplier 4 is successively converted by the resistors R1, R2 and the current inputted to the current- frequency converter circuit 6 and the output voltage ep2 of the multiplier 5 are successively converted by the resistors R1, R2. By this mechanism, the mutual balance error between powers can be brought to zero even if there is the relative error between the resistors R1, R2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a multiphase electronic watthour meter that measures multiphase power from a plurality of powers measured for each phase.

In a multi-phase electronic watt-hour meter that measures multi-phase electric energy from the electric power of each phase, it goes without saying that a voltage transformer and a current transformer are installed for each phase, but theoretically each phase can be shared. Multipliers that can do this are also usually provided separately. this is,
In particular, in multipliers using recent integrated circuits, the previous results remain in each chip, so if each phase is shared, the results of each phase will influence each other and errors will occur. This is because it will occur.

FIG. 1 shows a conventional three-phase electronic watt-hour meter in which multipliers are provided for each phase. 1, 2.3 are power distribution lines, PT+
, PT2 is a potential transformer, C'T, .

CT'2 is a current transformer; 4.5 is a multiplier; A voltage e1m generated by receiving a current proportional to the current flowing through the distribution line 1 by the current transformer CTI and receiving it by the current transformer burden resistor RLI is input.

The multiplier 4 outputs a voltage ePl proportional to the instantaneous power. Similarly, the multiplier 5 receives a voltage eV2 which is stepped down in proportion to the voltage between the distribution lines 2 and 3 by the potential transformer PT2,
A voltage e12 generated by receiving a current lowered by the current transformer CT2 in proportion to the current flowing through the distribution line 3 by the current transformer negative resistor RL2 is inputted to the multiplier 5.
outputs a voltage eP2 proportional to the instantaneous power. voltage ep
l+ept are input to the current frequency conversion circuit 6 through resistors R, , R, respectively, and the currents are combined at a virtual ground point provided in the current frequency conversion circuit 6, resulting in a combined current Ipt.
A pulse train proportional to f. is output from the current frequency conversion circuit 6. At this time, the composite current ■1. is expressed by the following formula.

At this time, a balance error ε between the two powers occurs. These six balance errors are expressed by the following linear equation, assuming that the voltage ep) + ep2 is accurate and s ep+ =ep2=ep.

apl ep2 R, Rt In this way, in the conventional multiphase electronic watt-hour meter, the 1 multiplier 4.5 generates a voltage ep+ * that is exactly proportional to the power.
Even if ept is obtained, a relative error in the resistances R, , R, which are originally set to the same value causes a balance error εa between the powers. In other words, even though the load is actually a balanced load, it may be mistakenly measured as an unbalanced load. Therefore, since it cannot be used as an electric IT meter as it is, conventionally, an adjusting means such as a variable resistor is provided to adjust the resistance value, and the resistance Et, , R is adjusted.

It eliminates relative errors and is used in an accurately balanced manner. However, this type of adjustment requires experience and is troublesome to operate.

The object of the present invention is to solve the above-mentioned problems.

Multi-phase electronic power converts the output voltage of each phase multiplier into a 1°C current.Even if there is a relative error between each resistor, the balance error between power sources can be eliminated without the need for adjustment. The purpose is to provide a meter.

In order to achieve this object, the present invention provides a switching means that switches the connection relationship between the multiplier and each resistor that converts the output voltage of the multiplier for each phase into a current at regular intervals, and repeats the switching. , here.

The current value for each phase flowing into the virtual ground point of the current frequency conversion circuit is set to the average value of the currents obtained by sequentially converting the output voltage of the multiplier for each phase using the resistor.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 2 shows an embodiment of the invention that is three-phase. 1st
Parts that are the same as those in the figures are designated by the same reference numerals.

In Figure 2, 7 is a comparator, R, , R4 is a feedback resistor, 8 is a T-type 7 lip-flop, 9, 10.11.1
2 is an analog switch, and 1 or more correspond to the switching means of the present invention. Comparator 7 and feedback resistor R, , R,
constitutes a zero-cross comparator, and the inverting input terminal of comparator 7 is connected to the output voltage ev of the potential transformer PT.
1 is input, the output of comparator 7 is the voltage e
When v1 is 07 or more, it is a low level, and when it is 0■ or less, it is a high level, and this signal is input to the T-type flip 70 tube 8. Since the voltage evl is an AC voltage of 50 Hz to 60 Hz, the output of the T-shaped lip 70 and the knob 8 is 2
The polarity is reversed every 1 to 10 periods for a mark space of 5 Hz to 30 H2.

°R type rough flip-flop 8 output Q is at noise level, output level is low level for a certain period, analog switch 9, 1
2 is on and the analog switch 10.11 is off, the output voltage epH of the multiplier circuit 4 is applied to the resistor R2, and the output voltage e7 of the multiplier circuit 5 is applied to the resistor R, and is converted into a current. The currents are combined at the virtual ground point of the frequency conversion circuit 6. Further, the output Q of the T-type flip-flop 8 is at a low level, and the analog switches 10 and 11 are turned on for a certain period when the output Q is at a no-no level.

This is because analog switches 9 and 12 are turned off.

The output voltage of the multiplier circuit 4 is connected to the resistor R2, and the output voltage of the multiplier circuit 5 is connected to the resistor R2.
The output voltage ep2 of is applied to the resistor R1, respectively, and '1
The current is converted into a 1L flow, and the current is combined at the virtual ground point of the current frequency conversion circuit 6.

In this way, the resistors R and R6 connected to the 1 multiplier 4.5
are exchanged at regular intervals, and this exchange is repeated, so that the output voltage apl of the multiplier 4 becomes equal to the resistance R, , It2
The current input to the current frequency conversion circuit 6 and the output voltage ep2 of the 1 multiplier 5 are sequentially converted by the resistors It, ,
The composite current ■it, which is sequentially converted by the current input to the current frequency conversion circuit 6, is accumulated over a certain period of time.

At this time, the balance error ε: is expressed by the following linear equation, assuming that the voltage e, 1°ep2 is accurate, and ePt =ep2''ep.

= Of4) As described above, according to the present invention, even if there is a relative error between the resistors R1 and R7, the balance error between the electric powers can be made zero.

The case of the three-wire type three-phase electronic power amount needle has been described above, but FIG. 3 shows the case of the four-wire type.

Another embodiment of the invention is shown. The same parts as in FIG. 2 are designated by the same reference numerals. Moreover, FIG. 4 is a time chart showing signal states in each part of the circuit of FIG. 3. Third
In the figure, 13 is the neutral wire of the distribution line, 14 is the multiplier, 1
5.16 is a JK type flip-flop 17 is an AND gate.

18 to 26 are analog switches, PT is a voltage transformer, CTs is a current transformer, R1 is a resistor, ]R1, * is the current transformer burden resistance %, and 1 is the power supply voltage. In Figure 3,
Comparator 7, resistor R3, R,, JK type flip-flop 15.16. And gate 17. The analog switches 18 to 26 correspond to the switching means of the present invention. The signal states of each part in this switching means are as shown in FIG.
1, the signal T2 which is the Q output of the JKK flip-flop 16, and the signal T3 which is the output of the AND gate 17.

The signals are a one-to-two mark space signal that is shifted in phase or period from each other. (No. i T, high level, signals T2 and T,
When is low level, analog switch 1B, 22.2
6 is on and the others are off.

Output voltage of multipliers 4, 5.14 epl+ ep> +
eps are applied to resistors R, 11, 2, and B, respectively. C when the signal T2 is at high level and the signal Ts and TI are at low level.

When the analog switches 19, 23, and 24 are on and the others are off, a voltage eM + ePt * eps is applied to the resistors R2, R, , , R, respectively. Signal T3 is high level.

When the signals T and T are at low level, the analog switches 20, 21, and 25 are on, the others are off, and the voltage eP1
+ ept + ep3 are the resistances R,, R,, R, respectively
, is applied to .

Thus, the resistor R2 connected to the multiplier 4.5.14
, R7 and R6 are exchanged every fixed period corresponding to the mark period of the signals T1 to T, and this exchange is repeated, similar to the case of the 3m type.

The current value for each phase flowing into the virtual ground point of the current frequency conversion circuit 6 is the output voltage epl of the multiplier 4.5.14 for each phase.
1ept + e++3 each with a resistor R,,B,,I
This is the average value of the three current values sequentially converted by t.

At this time, the balance error is the voltage e+++ + epz *
If eps is accurate, it will be 0.

Note that in both the three-wire and four-wire embodiments described above, the signal input to the inverting input terminal of the comparator 7 is the output evl of the transformer PT, but it is also possible to use a signal of another frequency. Of course, this is also possible.

As explained above, according to the present invention, the connection relationship between the multiplier and each resistor that converts the output voltage of the multiplier for each phase into a current is changed at regular intervals.

A switching means is provided that repeats the switching, so that the current value for each phase flowing into the virtual ground point of the current frequency conversion circuit is made the average value of the current obtained by sequentially converting the output voltage of the multiplier for each phase using the resistor. Therefore, even if there is a relative error between the resistors that convert the output voltage of the multiplier for each phase into a current, the balance error between the power sources can be eliminated without requiring adjustment.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional three-phase three-wire electronic power meter, Fig. 2 is a block diagram of a three-phase three-wire electronic watt-hour meter that is an embodiment of the present invention, and Fig. 3 is a block diagram of a conventional three-phase three-wire electronic power meter. FIG. 4 is a block diagram of a three-phase 4m electronic watt-hour meter which is another embodiment of the present invention, and is a time chart showing signal states in each part of the embodiment of FIG. 4.5.14... Multiplier, 6... Current frequency conversion circuit, 7... Comparator, 8... T-type flip-flop, 9-12. 18-26... Analog switch,
15.16...JK type flip-flop 17.
...andgate, R,,R,. R, 1,, resistance, R,, R,...feedback resistance + epl -
eP2 * eP9...Output voltage of each multiplier, fo.
...Pulse train. Patent applicant: Tokyo Electric Power Company, Inc. (1 person) Minoru Nakamura Figure 1 Figure 2

Claims (1)

[Claims] 1. Outputs a voltage proportional to the load voltage and load current. It has a multiplier provided for each phase, a resistor that converts the output voltage of each multiplier into a current, and a virtual ground point inside, and the currents are combined at the virtual ground point and proportional to one composite current. A polyphase electronic watt-hour meter equipped with a current frequency conversion circuit that outputs a pulse train, characterized in that a switching means is provided that switches the connection relationship between the resistor and the multiplier every fixed period and repeats the switching. A multi-phase electronic watt-hour meter.