CN201229849Y - External integral Rogowski coil current transformer - Google Patents

Abstract

The utility model relates to an outer integral Rogowski coil current transformer. The Rogowski coil is wound on the ring-shaped nonmagnetic framework in a circumferentially and uniformly distributed manner, a primary current conductor passes through the axis of the ring-shaped coil, a reactor with proper inductance and a secondary load resistor are connected in series between two outgoing line terminals of the coil, an input resistor of a secondary electronic equipment circuit is also included in the load resistor, compensation capacitors are connected in parallel at two ends of the secondary load resistor to compensate the phase of voltage at two ends of the resistor, and the error requirement of the electronic current transformer for protection is finally met through parameter fine adjustment of the load resistor and the compensation capacitors. The high-voltage power grid fault current protection device has the advantages of being novel in structure, overcoming the limitation that the internal integral Rogowski coil current transformer is used for large current, enabling the current transformer to be used for fault current protection of a high-voltage power grid, and enabling the current to reach 10 kA-100 kA generally.

Description

A Rogowski Coil Current Transformer with External Integral

technical field

The utility model relates to a current transformer, in particular to an electronic current transformer using a Rogowski coil, and belongs to the technical field of power transformers.

Background technique

At present, current transformers are widely used in 110kV and above power grids for line and equipment protection. The traditional current transformer is manufactured according to GB 1208 "Current Transformer". It consists of an iron core and primary and secondary windings wound on the iron core. It works by the principle of electromagnetic induction, and the secondary rated current is 5A and 1A. The electronic current transformer is manufactured according to GB/T 20840.8 "Transformer Part 8: Electronic Current Transformer". Its secondary analog output voltage rating does not exceed 4V, and the secondary rated voltage is generally 225mV for protection. It can be directly used as the input signal of the secondary electronic equipment circuit. There are two types of electronic current transformers that use Rogowski coils and have in-phase output: external integral and internal integral. The Rogowski coil of the external integral current transformer has a large enough resistance, and the current of the secondary circuit is converted into a voltage with the same phase as the primary current through the capacitance integration circuit connected outside the coil, and the internal integral current transformer The Rogowski coil has a large enough self-inductance, and the voltage with the same phase as the primary current can be obtained on the secondary load resistor with small resistance. The advantage of the Rogowski coil current transformer is that it will not cause magnetic saturation due to the DC component in the primary current and the excessive primary short-circuit current, which is especially beneficial for the transient protection of the line. However, the external integral Rogowski coil current transformer needs to use an electronic amplifier, which reduces the reliability of the current transformer; while the Rogowski coil current transformer using the internal integral phase shift is used for large currents, due to the coil The self-inductance is small, and the phase shift error is large, which cannot meet the accuracy requirements of use, and the use range is limited.

Contents of the invention

The utility model provides an external integral type Rogowski coil current transformer to improve the accuracy of the large current Rogowski coil current transformer with internal integral phase shifting and avoid the use of electronic amplifiers. In principle, the transformer is an internal integral phase shifter, but it is not limited by the self-inductance of the coil. It has higher reliability than the external integral Rogowski coil current transformer using an electronic amplifier.

The technical scheme adopted by the utility model is: a reactor and a secondary load resistance are connected in series between the two outlet terminals of the Rogowski coil, and a phase compensation capacitor is connected in parallel at both ends of the secondary load resistance.

In the utility model, the Rogowski coil is wound on the non-magnetic frame of the circular ring in a manner of uniform distribution on the circumference, and the primary current conductor passes along the axis of the circular coil.

罗果夫斯基线圈的互感为M，自感为L₀，50Hz下等效损耗电阻为R₀，二次感应电势为 ${\stackrel{\·}{E}}_2=-\mathrm{j\ωM}{\stackrel{\·}{I}}_1,$ 电抗器的电感量为L_m，50Hz下等效损耗电阻为R_m，二次负荷电阻的阻值为R_b，补偿电容器的电容量为C_b，二次电压输出为：The electrical principle of this technical solution can be illustrated by the equivalent circuit in FIG. 2 . The primary current in the figure is

The mutual inductance of the Rogowski coil is M, the self-inductance is L ₀ , the equivalent loss resistance at 50Hz is R ₀ , and the secondary induced potential is ${\stackrel{\&Center\; Dot;}{\mathrm{E.}}}_2=-\mathrm{j\ωM}{\stackrel{\&Center\; Dot;}{I}}_1,$ The inductance of the reactor is L _m , the equivalent loss resistance at 50Hz is R _m , the resistance of the secondary load resistance is R _b , the capacitance of the compensation capacitor is C _b , and the secondary voltage output is:

${\stackrel{<span\; class="notranslate">\; \&CenterDot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;M</span>}{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}$

$<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;M</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span>}$

When R _b +R ₀ +R _m ＝ω ² (L ₀ +L _m )R _b C _b , the phase is fully compensated, then:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; MR</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}$

The beneficial effect of the utility model is that the structure is novel, and it overcomes the restriction that the inner integral Rogowski coil current transformer is used for a large current, so that it can be used for the fault current protection of the high-voltage power grid, and the current usually reaches 10kA to 100kA .

Description of drawings

Fig. 1 is a schematic circuit diagram of the utility model.

Fig. 2 is an equivalent circuit diagram of the utility model.

In the figure: 1. Primary current conductor, 2. Ring non-magnetic skeleton, 3. Rogowski coil, 4. Reactor, 5. Secondary load resistance, 6. Secondary voltage output terminal, 7. Phase compensation capacitor.

Detailed ways

In Fig. 1, the Rogowski coil 3 is wound on the ring non-magnetic frame 2 in a uniform manner around the circumference, the primary current conductor 1 passes along the axis of the ring coil, and is connected in series between the two outgoing terminals of the coil The reactor 4 and the secondary load resistance 5 are connected, and the compensation capacitor 7 is connected in parallel at both ends of the secondary load resistance. close to agreement.

In one embodiment of Fig. 1, the primary current conductor 1 flows through the power frequency current 2500A, the structure of the Rogowski coil 2 is that the circumference is evenly distributed and wound 2500 turns on the plastic ring of φ495×420×70, and the winding The DC resistance is 25Ω, the induced voltage is 4.6V, and the coil secondary circuit is connected in series with a reactor 4 with a reactance value of 2000Ω and a secondary load resistor 5 with a resistance value of 100Ω. The input resistance of the secondary electronic equipment circuit is also included in the load resistor 5, and the reactance The equivalent loss resistance of the resistor 4 at 50Hz is 60Ω, and a 3μF capacitor 7 is connected in parallel at both ends of the resistor, and a voltage output of about 225mV that is close to the same phase as the primary current is obtained on the secondary voltage output terminal 6, and then through the pair of resistors The fine-tuning of the parameters of 5 and capacitor 7 finally meets the error requirements of the 0.5-level electronic current transformer for protection.

Claims (2)

1, a kind of outer integration type rogowski coil current transformer is characterized in that: series connection inserts reactor and secondary load resistance between two outlet terminals of rogowski coil, the phase compensation capacitor in parallel at these secondary load resistance two ends.

2, outer integration type rogowski coil current transformer according to claim 1, it is characterized in that: rogowski coil is wound on annulus in the circumference uniform distribution mode not to be had on the magnetic skeleton, and the primary current conductor passes along this Circumferential coils axis.

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