CN203849330U - DC Resistance Meter for AC Current Loops - Google Patents

Abstract

The utility model discloses a direct resistance measuring device for an alternating current circuit, which comprises: four contacts, respectively contact one, contact two, contact three and contact four; four test lines, respectively connected to The four contacts are electrically connected; and a diverter switch, which has four switching gear positions, including neutral, a first gear for making contacts one and four, and a second position for making contacts two and four. Gear position, the third gear position of connecting contact three and contact four, when using the DC resistance measuring device according to the utility model to measure the AC current loop, only need to plug and unplug the multimeter connection twice, that is (measure CT side DC resistance once when measuring the direct resistance of the cable side), which greatly simplifies the measurement steps, shortens the measurement time, and improves work efficiency.

Description

DC Resistance Meter for AC Current Loops

technical field

The utility model relates to a direct resistance measuring device for an alternating current loop.

Background technique

The direct resistance measurement of the secondary AC current loop of a current transformer (CT) is an indispensable test item in the maintenance pre-test of the State Grid Power Supply Company, that is, the measurement of the three-phase DC resistance in the secondary current loop of the CT. Among them, the DC resistance is described in this paper can be referred to as direct resistance. When measuring, the current slider in the switch terminal box must be opened, and the direct resistance of the CT side (also called under the panel in practical applications) and the cable side (also called on the panel in practical applications) should be measured respectively. DC resistance test (that is, current transformer (CT) secondary AC current loop direct resistance measurement) can check whether the welding quality of the internal wire of the current transformer winding, the welding quality of the lead wire and the winding, and the specification of the wire used for the winding meet the design requirements , Whether the three-phase resistance is balanced (that is, whether the three-phase direct resistance meets the three-phase direct resistance balance), etc., play an important role in ensuring the safe operation of the power system. The three-phase direct resistance on the same side (on the CT side or the cable side) must meet the three-phase direct resistance balance, that is, satisfy the following formula: (maximum direct resistance-minimum direct resistance)/maximum direct resistance*100%＜ 10%, that is, the error requirement within 10% should be met. As shown in Figure 1, it is a schematic diagram of the secondary AC current circuit of a current transformer (CT), where E is the CT side, and D is the three current transformers (respectively Phase A, Phase B, Phase C), H is the terminal box, J is the slider group (also called the current loop terminal block slider group), I is the contact of the slider, F is the cable side, G is the protective device. The slider group includes four sliders Ⅰ, Ⅱ, Ⅲ, and Ⅳ. Each slider is divided into two parts 1 and 2. The CT side has A-phase current transformer, B-phase current transformer, and C-phase current transformer. The devices are electrically connected to slider I-1, slider II-1, and slider III-1 respectively, and the N wire (current loop N-pole lead wire) on the CT side is connected to slider IV-1; the protection device on the cable side is also connected to the slider IV-1. It has A phase, B phase, and C phase, which are electrically connected to slider I-2, slider II-2, and slider III-2 respectively, and the N wire (current loop N pole lead wire) on the cable side is connected to the slider IV-2.

Under normal circumstances, the 1 and 2 parts of the slider are merged together (that is, electrically connected), and the phases of the CT side and the cable side are electrically connected respectively, so that the circuit can work normally. When it is necessary to measure the direct resistance, open the 1 and 2 parts of the slider (that is, disconnect, shown by the double-headed arrow and the dotted line in the terminal box H in Figure 1), taking the measurement of the A-phase direct resistance on the CT side as an example, through Insert the negative wire of the multimeter into the contact I of the slider Ⅳ-1, and then insert the positive wire of the multimeter into the contact I of the slider Ⅰ-1 to obtain the direct resistance of phase A on the CT side. Measure the A-N, B-N, and C-N single-phase direct resistance on the CT side and the cable side. If the three-phase current direct resistance value on the same side meets the direct resistance requirement in terms of resistance value and meets the three-phase balance requirement, that is, the resistance value of a single direct resistance on each side needs to meet the requirements (usually a few ohms), It is qualified only if it meets the three-phase direct resistance balance requirements described above.

Since the multimeter can only measure single-phase direct resistance each time, when using the traditional measurement scheme for measurement, it is necessary to repeatedly plug and unplug the positive wire of the multimeter to connect the three phases on different sides. False and other problems, resulting in measurement errors caused by artificially plugging and unplugging the wiring. The current loops on both sides (CT side and cable side) have to be plugged and unplugged six times in total. In the pre-test of the power supply company, each line or main transformer interval has more than four sets of AC current loops, so the traditional measurement scheme is used. The process of DC resistance measurement is cumbersome and inefficient, and the terminal block is plugged and pulled out many times, which will cause unnecessary damage to the terminal block jack.

Utility model content

The problem to be solved by the utility model is that it is cumbersome and inefficient to use a multimeter to directly measure the direct resistance of the AC current loop, and a direct resistance measuring device for the alternating current circuit is provided, through which the multimeter can measure the direct resistance of the alternating current circuit. The direct resistance measurement can improve the measurement efficiency.

In order to solve the above problems, the utility model provides a direct resistance measuring device for an alternating current loop.

Wherein, the direct resistance measuring device includes:

Four contacts, namely contact one, contact two, contact three and contact four;

four test leads electrically connected to the four contacts; and

The diverter switch has four switching gear positions, including neutral gear, the first gear position of making contact one and contact four, the second gear position of making contact two and contact four, and making contact three and the third gear of contact four.

Preferably, the test line is a DCC series power test lead.

Preferably, each of the four contacts includes binding posts, and the first gear, the second gear and the third gear of the diverter switch correspond to the connecting posts of contact one and contact four, contact two and contact four respectively. The terminal for point four and the terminals for contacts three and four.

As preferably, the direct resistance measuring device further includes:

The measurement box, the four contacts and the changeover switch are located in the measurement box, and the surface of the measurement box has openings for four test lines to protrude from.

Preferably, the measuring box is provided with a dial for switching the switch to four switching positions, and the measuring box has marks indicating the four switching positions.

Preferably, the measurement box is a thin square box body, including opposite square top and bottom surfaces, and four sides; the top surface is provided with dials and marks, and the side surfaces are provided with openings.

Preferably, the free end of each test wire is provided with a plug joint and a connection clip.

The utility model has the beneficial effects relative to the prior art in that:

1. When using the direct resistance measuring device according to the present invention to measure the AC current loop, it is only necessary to plug and unplug the multimeter wiring twice, that is (once when measuring the direct resistance on the CT side and once when measuring the direct resistance on the cable side), which greatly simplifies the measurement Steps, shorten the measurement time, improve work efficiency;

2. The direct resistance measuring device according to the utility model does not need frequent plugging and unplugging test wiring, which can avoid measurement errors caused by artificial plugging and unplugging wiring, is easy to apply, can be used repeatedly, and improves the accuracy of measurement results.

Description of drawings

FIG. 1 is a schematic diagram of direct resistance measurement of an AC current loop in the prior art;

Fig. 2 is a schematic structural view of an AC current loop direct resistance measuring device according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of the internal wiring of the direct resistance measuring device shown in Fig. 2;

Fig. 4 is a schematic wiring diagram for measuring A-N phase direct resistance on the cable side by using the direct resistance measuring device of the embodiment of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in detail. Wherein, the same reference numerals represent the same components in different drawings.

According to an embodiment of the present invention, a kind of direct resistance measuring device for alternating current loop is provided, as shown in Figure 2, it is a schematic diagram of the outside of the direct resistance measuring device for alternating current circuit according to the present invention , as shown in FIG. 3 , which is a schematic diagram of the internal wiring of the direct resistance measuring device shown in FIG. 2 . The direct resistance measuring device used for the AC current loop will be described below with reference to FIG. 2 and FIG. 3 . Wherein, the direct resistance measuring device includes four contacts, four test wires and a changeover switch, wherein, the four contacts are respectively contact one (shown as α in Fig. 3 ), contact two (shown as α in Fig. 3 Shown as β in ), contact three (shown as γ in Figure 3) and contact four (shown as δ in Figure 3); four test wires, shown in both Figures 2 and 3 They are L-α, L-β, L-γ and L-δ, which are electrically connected to four contacts respectively; switch switch, which has four switching positions, including neutral gear, contact one and contact one respectively. The first gear of four, the second gear of making contacts two and four of contacts, the third gear of making contacts three and four of contacts. In other words, one end of the switch is connected to contact four, and the other end of the switch can be switched to be connected to contact one (that is, corresponding to the first gear), contact two (that is, corresponding to the second gear) position), contact three (corresponding to the third gear), or neutral. The four contacts each include binding posts, and the first gear, second gear and third gear of the diverter switch correspond to the connecting posts of contact one and contact four, and the terminals of contact two and contact four respectively. Terminals and terminals for contacts three and four. In case of damage to the test lead, the test lead can be replaced. The four contact points can also be fixedly welded with one end of the test line, thereby increasing the reliability of the contact. In addition, the free end of each test line is provided with a plug connector and a clamp for connection with the AC current loop that needs to measure the direct resistance.

The direct resistance measuring device according to the present utility model can further include: measuring box K (in Fig. 2 to Fig. 4, all show measuring box with K), four contacts and switch are positioned in measuring box K, and measuring box K The surface has openings through which four test wires can protrude, preferably, the number of openings is four. Preferably, the measuring box K is provided with a dial for switching the switch to four switching positions, and the measuring box K has marks indicating the four switching positions. Specifically, the measurement box K has a mark OFF (closed) representing neutral gear, and three marks α, β and γ respectively representing contact one, contact two and contact three (these three marks can be connected with The three test lines correspond one to one), that is, the total direct resistance measuring device has four gears. There is a mark sign on the shift bar outside the protruding measuring box K of the switch to show the pointing end of the shift bar and to indicate the state of the switch. As shown in Figure 3, the three positions of α, β and γ and L-δ correspond to the four terminals inside the measurement box K respectively, and each terminal is connected to a test line. When the sign end of the switch points to α, it means L-δ and L-α; when the sign end of the switch points to β, it means L-δ and L-β; when the sign end of the switch points to γ, It means L-γ and L-α. When the sign end of the switch points to OFF, it means that L-δ is not connected to any wire. In practical applications, the four test lines can be distinguished by different colors, for example, the colors of the four test lines can be yellow, green, red, and black. In the embodiment of the present utility model, the test lines can all adopt the DCC series power test leads specially used for measuring the direct resistance of the AC current loop through relay protection. The test line, also known as the test lead, is a special test line for the power system maintenance test. It is suitable for relay protection sites, laboratories and other test and debugging places. It has the characteristics of convenient connection (just plug and pull connection, no need to open the device), small contact resistance, soft wire, and good insulation performance. The DCC series power test wires are composed of multi-strand flexible wires, which are special test wires for power system relay protection. They have the characteristics of softness, high pressure resistance, high strength, and good toughness. In the field of relay protection, laboratory and other test and debugging sites, it can meet the requirements of direct resistance test. The connectors of the test leads match the specifications of the positive and negative jacks of the multimeter. Among them, the three test lines L-α, L-β, and L-γ (yellow, green, and red test lines) are on one side, and are drawn out from the top of the measurement box K through holes, and are used for equal intervals with substation lines or main transformers. The terminal blocks A, B, and C of the AC current loop in the switch terminal box are connected in three phases. The L-δ test line is drawn out from the hole on the other side of the measurement box K, and is connected to the positive pole of the multimeter when measuring the direct resistance. In addition, the measurement box K is a thin square box body, including opposite square top and bottom surfaces, and four sides; the top surface is provided with the dial and the mark, and the sides are provided with the opening. Optionally, the external dimensions of the measurement box K can be: 7-9 cm in length, 7-9 cm in width, and 3-4.5 cm in height, which can be easily carried by the staff. In a preferred embodiment, the size of the measuring box K is: length 8.2 cm, width 8.2 cm, height 3.8 cm.

As shown in FIG. 4 , it is a schematic wiring diagram for measuring the A-N phase direct resistance on the cable side by using the direct resistance measuring device of the embodiment of the present invention. Among them, Multimeter is the multimeter, Resis. is the resistance file of the multimeter, Port-P is the positive terminal jack, Port-N is the negative terminal jack, and L-N is the negative test line. Among them, the method of using a multimeter to measure the A-N phase direct resistance of the cable side through a direct resistance measuring device includes: first, connecting the L-δ test line of the tester to the positive terminal jack of the multimeter (that is, the L-δ test line of the tester As a universal positive test line), a negative test line is connected to the negative end of the multimeter, and the other end of the negative test line is connected to the N pole of the current loop. After the test wires at both ends of the multimeter are connected, adjust the multimeter to the resistance gear and the direct resistance measuring device to the OFF end to complete the preparation for the measurement. The specific operation method of the measurement is as follows. First, open the sliders of the terminal blocks I, II, III and IV, so that the AC current loop is divided into the CT side (under the panel) and the cable side (on the panel), that is, the current on both sides is cut off. open.

Insert the L-α, L-β, L-γ test wires of the direct resistance measuring device into the jacks of terminal block I-1, II-1 and III-1 respectively so that the three test wires of the direct resistance measuring device are electrically connected to the cable respectively. Phase A, phase B and phase C on the side, and the negative test line of the multimeter are connected to the socket IV-1 of the terminal block. Then adjust the position of the switching switch of the test box of the direct resistance measuring device to α, then the multimeter is connected to the A phase on the cable side, and the multimeter displays the A-N phase direct resistance value on the cable side;

In addition, in an unshown embodiment, when the gear position of the switch is adjusted to β, the multimeter is connected to the B phase on the cable side, and the multimeter displays the B-N phase direct resistance value on the cable side; when it is adjusted to γ, the multimeter is connected to For phase C on the cable side, the multimeter will display the direct resistance value of phase C-N on the cable side, and when it is turned OFF, it will be disconnected. The method for measuring the CT side is the same as this, and will not be repeated here.

Specifically, as shown in Table 1, it is the corresponding relationship between the gear position and the connected phase.

Table 1

gear alpha B gamma OFF Turn on the phase A-N B-N C-N failed

With such an operation scheme, the direct resistance measurement can be completed only by plugging and unplugging the terminal block twice. However, in the traditional measurement scheme, since the positive end of the multimeter only has one positive test wire, it is necessary to repeatedly plug and unplug the terminal block at ports I, II, and III six times to complete the measurement of direct resistance. The process is cumbersome and the efficiency is low.

According to an embodiment of the present utility model, compared using the direct resistance measuring device according to the present utility model and the traditional measuring scheme to measure the measuring result of the direct resistance of the AC circuit, the comparison result is as shown in Table 2, it can be clearly seen from the data in the table , Use the AC current loop convenient measuring device to measure accurately and meet the actual engineering requirements.

Table 2

The above embodiments are only exemplary embodiments of the utility model, and are not used to limit the utility model, and the protection scope of the utility model is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the utility model within the spirit and protection scope of the utility model, and such modifications or equivalent replacements should also be deemed to fall within the protection scope of the utility model.

Claims (7)

1. A direct resistance measuring instrument for an alternating current loop, characterized in that, comprising: Four contacts, namely contact one, contact two, contact three and contact four; four test wires, respectively electrically connected to the four contacts; and A changeover switch, which has four switching gear positions, including neutral gear, the first gear position for connecting the first contact point and the fourth contact point, and the second gear position for connecting the second contact point and the fourth contact point. gear, the third gear that connects the third and fourth contacts. 2. The direct resistance measuring device for an AC current loop according to claim 1, wherein the test line is a DCC series power test lead. 3. The direct resistance measuring device for an AC current loop according to claim 1, wherein the four contacts all include binding posts respectively, and the first gear position and the second gear position of the changeover switch and the third gear respectively connect the connecting posts of the contact one and the contact four, the connecting posts of the contact two and the contact four, and the contact three and the contact four of the terminal. 4. the direct-resistance measuring device for alternating current loop according to claim 1, is characterized in that, further comprises: The measurement box, the four contacts and the switching switch are located in the measurement box, and the surface of the measurement box has an opening for the four test lines to protrude from. 5. The direct resistance measuring instrument for an alternating current circuit according to claim 4, wherein the measuring box is provided with a dial for switching the switch to four switch positions, and the There are marks on the measuring box that represent the four shift positions. 6. The direct resistance measuring device for an alternating current circuit according to claim 5, wherein the measuring box is a thin square box body, comprising opposite square top and bottom surfaces, and four sides; The top surface is provided with the dial and the mark, and the side is provided with the opening. 7. The direct resistance measuring device for an AC current loop according to claim 6, wherein the free end of each test line is provided with a plug connector and a clamp.