FI106226B - Resistive voltage sensor - Google Patents

Description

1 106226

Resistive voltage sensor

Field of the Invention

A resistive voltage sensor for use in particular for medium and / or high voltage measurements and to be arranged in a space containing an insulating medium pierced by a primary current conductor, for example in connection with some type of insulator comprising a voltage divider consisting of a resistor and a resistor. In a voltage division based voltage transducer, the resistor is attached to, for example, a component in the voltage measured by the electrode, for example a primary current conductor, and the resistor serves to provide the necessary voltage drop, while the resistor clips at its first end to the resistor. Voltage measurement is performed over the low resistance and the voltage is proportional to the ratio of the high and low resistance.

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Background of the Invention

Accordingly, the present invention relates to a resistive voltage distribution based voltage sensor, the most suitable application of which is medium and high voltage measurements. The sensor is arranged in connection with a component used, for example, in connection with a medium-20 or high-voltage switchgear, such as a support or lead-through insulator, a combination sensor, a part of a circuit breaker or the like. The sensor can be used for both indoor and outdoor installations. In the following, the invention will be described in conjunction with a support insulator, since this embodiment is likely to illustrate the applicability of the invention.

• · · '· *' Traditionally, in power distribution technology, current and voltage transformers have been used for medium and high voltage current and voltage measurements. However, they are usually large in size and heavy and thus difficult to integrate with other components. Particularly in disturbances, the measurement accuracy of the current transformers · * ·, 30 is substantially reduced due to saturation of the transformer core • · - ”. In addition to transformers, there are methods for measuring voltages that are ««. crossed between resistive voltage dividers, capacitive voltage dividers and optical sensors.

·· "'·' Increasing requirements for better measurement accuracy of measuring transducers favor the use of resistive elements 2 106226 as purely voltage measuring components of the transducers. The accuracy of resistive elements and measurement methods is better within the required voltage range and frequency than with capacitive measurement methods.

There are prior art solutions in which a resistive voltage divider based on a voltage divider 5 is integrated, for example, in connection with an insulator. In these solutions, the upper resistor of the voltage divider is generally implemented using a high voltage resistor. The problem with these solutions is the large size, high cost, rigid structure and rod-shaped shape of the high-voltage resistor, which makes it difficult to integrate the voltage divider with other components.

10 The voltage strength of such a solution also causes problems. The resistor of the voltage divider forms a channel within the voltage divider within the cast resin insulator, where a discontinuity point is created at the interface between the resistor and the insulator. Over time, small electrical partial discharges may occur at the interface, causing the casting resin to form in the cavity, impairing the insulation capacity of the 15 insulators, and may create a channel for excesses in the event of disturbances.

A problem with existing solutions is often the unfavorable shape of a voltage measuring transducer comprising a voltage divider, which results in fitting the transducer to another component, such as a support insulator, unnecessarily increasing the size of the component or impeding its advantageous design. The focus is constantly on smaller and more integrated components. Second, the voltage strength must be good enough for components with a typically lifetime of tens of years. For this reason, the insulation strengths should be sufficient and any electrical discontinuities in the structures should be minimized. Thirdly, the requirements for measuring accuracy ·: * ·: 25 increase, so that a purely resistive measuring sensor gives a precise measurement over a wide frequency band and is not sensitive to environmental disturbances. Fourth, the known voltage measurement solutions based on measuring transformers or high-voltage resistors are expensive. The high voltage resistor has a rigid structure and its coefficient of thermal expansion differs from the coefficient of expansion of the casting resin, which causes stress in the resin. Sixth, the shrinkage of the casting resin after casting, and in addition, over time, causes tension in the high-voltage resistor and resin ·: * ·: interface.

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Brief Description of the Invention

An object of the invention is to provide a voltage sensor based on a resistive voltage divider so that the above problems can be solved. This is achieved by a resistive voltage sensor of the type disclosed in the introduction, characterized in that the top and bottom resistors of the voltage divider comprise a resistor chain arranged in a substantially helical shape around the primary current conductor.

Preferred embodiments of the invention are set forth in the dependent claims.

The invention is based on making a high-voltage resistor of one or more elements of a resistive material, preferably low voltage resistors, for example, and joining the elements together, i.e. by chaining, to form a complete resistor to provide the required resistance. . This resistor chain is bent to a series of resists of advantageous length relative to the outer dimensions of the tu-twist, which are arranged - pleated - side by side. The folded resistor chain thus formed is formed around the primary current conductor of the bushing, viewed from the cross-sectional direction of the bushing, in the shape of a spiral 20, such that the first end of the voltage divider is The other is the lower resistor: the end is fixed with an electrode to ground potential.

By arranging a resistor chain forming a voltage divider around the primary current conductor in the insulating medium in a substantially helical form: T: such that the resistively distributed potential of each point of the resistor chain is: * · *: substantially equal to the corresponding capacitively distributed electrical field of the insulating medium miniature ···. • Voltage-sensitive and fault-tolerant voltage measuring sensor that can be fitted to the • • 30 winder. The structure of the voltage transducer is called *: * a discrete pleated voltage divider structure in the support insulator. In addition, the small size of the voltage sensor also allows other measuring sensors to be fitted to the same “*” · support insulator without significantly increasing the size of the insulator.

, The voltage divider, built of series-connected separate resistors • «· 35, becomes easily shaped and flexible.

• · *** The advantage of this is that the size and shape of the sensor can be flexibly modified, 4 106226, when the sensor is fitted to a support insulator or other similar component. By using as purely resistive components as possible and arranging a resistor chain in a spiral form as claimed, the effect of capacitive and inductive environmental factors on the sensor is minimized.

Another advantage of the discrete pleated voltage divider structure is that the elasticity, and hence the mechanical resistance, of such a structure is substantially superior to rigid rod-shaped resistor structures. The ribbon-like resistor chain of the pleated voltage divider structure withstands the shrinkage of the casting resin after casting, as well as the stresses exerted by the thermal expansion on the voltage divider caused by temperature variations.

The advantage of using low voltage resistors is that the sensor according to the invention becomes cheap. Low voltage resistors are available from several manufacturers in a variety of accuracy, quality and price ranges, making it easy to manufacture sensors with the required features by selecting their components according to their requirements. If it is required to manufacture a particularly small voltage transducer, the transducer according to the invention can also advantageously be implemented using surface coupling resistors.

The resistance components of the high and low resistors of the voltage sensor according to the invention are arranged parallel to the primary current conductor. As a result, the levels of the individual silicons of the resistive elements comprising coil-like structures are parallel to the magnetic field caused by the current flowing in the primary current conductor, thereby minimizing interference in the resistive element of the magnetic field, which gives an advantage *: * ·: and the sensitivity to interference is reduced.

: T: The resistor elements of the voltage divider upper and lower resistors are arranged in a series of resistors comprising one or more successive resistor elements, which are bent parallel to each other and to the primary current conductor ... ·. parallel. Such an arrangement allows the sensor to be shaped preferably according to the component to which it is fitted, while maintaining *: * 'the accuracy and small size of the sensor.

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When the Resistor Kits consisting of separate resistor elements are: ·: ··: advantageous from the transverse direction of the primary current conductor to the form of a spiral en-. with a spiral support structure made of insulating material around the flow conductor, if necessary, the advantage is that the optimally designed spiral structure of the resistor chain is retained during the manufacturing process of the sensor when the sensor is molded into an insulating material such as a casting resin, connection. The length of the channel formed by the support structure to the insulating material - the crawl distance - can also be significantly adjusted by the advantageous design of the support structure. When the creep distance 5 is substantially longer than the radius between the inner surface resting against the primary current conductor of the insulating body and the outer surface of the body, the spiral support structure supporting the resistor chain is good voltage strength, and thus the effective life of the sensor is significantly increased.

Further, when the spiral resistor chain comprising the upper and lower resistors of the voltage divider according to the invention is arranged in a thread around the primary current conductor, in structures where the elongated shape of the transducer 15 is advantageous, more flexibility in transducing the transducer may be obtained.

By coupling a capacitor component in parallel with the low resistor of the voltage divider, dimensioned according to the characteristics required of the sensor and the intended operating environment, the effects of stray capacitance * and 'inductance' between the resistor elements and the primary current conductor and between the resistor elements can be significantly frequency characteristics and accuracy. Further, the effect of stray capacitance and ambient interference on the sensor measurement accuracy can be advantageously reduced by designing the sensor connector electrodes to act as electric field controllers.

** Brief Description of the Drawings

The invention will now be described in more detail in connection with some preferred embodiments of the invention with reference to the accompanying drawings, in which: Fig. 1 shows a transverse section through a support insulator adapted to an exemplary embodiment of the invention; · · Spiral shaped resistive voltage sensor, *. Fig. 2 shows a longitudinal sectional view of the support insulator of Fig. 1 and the voltage supply fitted thereto; Fig. 3Α shows an advantageous folding structure of the resistor chain forming the voltage transducer of Figs. and Fig. 3B shows the structure of Fig. 3A as seen in the transverse direction.

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DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 2 show an embodiment of a resistive voltage sensor according to the invention. In this embodiment, the sensor is arranged in connection with a support insulator. The insulator comprises a body having a space 1 in which the insulating medium 10 is contained. The insulating medium is preferably a casting resin, but may also be a gas. The body is pierced by a cylindrical primary current conductor 2. The primary current conductor 2 is at a voltage specific to the voltage range in question and the voltage measurement by a sensor according to the invention is directed to the voltage of the primary current conductor 2. Depending on the intended use of the insulator 15, the insulator body may have several layers.

The voltage divider based on the voltage divider according to the invention is functionally a voltage divider comprising a resistor circuit forming an upper resistor and a lower resistor. The purpose of the upper resistor is to provide the necessary voltage drop, while the lower resistor serves as a measuring element over which the measurement of the ridge-20 thread is performed. The voltage to be measured is proportional to the ratio of the resistances of the upper and lower voltages. The upper resistor is connected, for example, by an electrode 3 at its first end to the primary current conductor 2 and at its second end *: ··: to the lower resistor. The lower resistor is attached at its first end to the upper · · · · ·: and at its second end with the electrode 4 to the ground potential. In addition, between the lower resistor and the upper resistor 25, there is a third electrode which provides a voltage measurement signal.

In Fig. 1, a voltage sensor according to the invention is disposed on the insulating layer * ::: in the direct contact conductor 2 of the insulator ... with a space between the inner surface 8 and the outer surface 9 of the insulating material. The strength of this insulating layer is 30 mm - the radius between the inner surface 8 and the outer surface 9 - in 20 kV: *** devices, for example, preferably 20 mm. In the cross-sectional view of Fig. 1, the transverse direction of the insulator *: 'shows a spiral shape of the resistor chain 6 \ forming the voltage sensor. Figure 2, on the other hand, shows the positioning and construction of the resistor circuit 6 constituting the voltage sensor as a cross-section of the insulator in the longitudinal direction of the primary current conductor 2.

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Figure 3A shows that the discrete resistive voltage transducer according to the invention preferably consists of a series of low voltage resistor elements 5 used in electronics, thus forming a resistor circuit 6. In 20 kV devices, the upper resistor of a voltage divider may advantageously consist of, for example, 100 has a total resistance of 100 ΜΩ. The resistance of the low resistance may preferably be, for example, 10 kn.

Figure 3A shows an example of bending of the resistor chain 6. Folding refers to bending a resistor chain 6 such that a series of resistor lengths of one or more successive resistor elements is formed from the resistor 10 chain - in the embodiment there are two successive resistor elements - which are bent into parallel pleats, and the length of the ribbon structure Referring to Figures 1 and 2, it is shown how the voltage sensor formed in the above manner is wound around a live primary current conductor 2.

The voltage sensor of the invention is characterized by its helical shape around the primary current conductor 2. In the insulator structure of the embodiment, the pleated resistor chain 6 is wound helically around the primary current conductor 2 of the insulator 20 structure. In the voltage sensor according to the invention, the resistor chain 6 is shaped such that the potential at each point of the resistor chain 6 constituting the voltage divider is equal to or nearly the same as the capacitive voltage distribution potential of the corresponding point of the insulating material of the supporting insulator.

The optimum helical path of the pleated resistor chain 6 in the insulation around the primary current conductor 2 can be formed mathematically.

: * · *: The intensity of the electric field surrounding the primary current conductor 2 in the space between the inner surface 8 and the outer surface 9 of the dielectric material at point r is • · · · · 30 Er = - dvr / dr,

• * III

··· • · · where r is the radius of the cylinder surface measured from the midpoint of the primary current conductor 2 and Vr is the electric field potential in the corresponding material of the insulating layer. ! ·. point. By integrating with respect to r ::: 35 • · • ·

III

e 106226 r

Vr = -JE * dr r0 5 gives the following modeling for the radius r of the optimal path [(U * ln (r0) - In (r0 / n) * Vr) / U] r = e, 10 where U is the voltage of the primary current line 2, r0 radius of outer sheath 9 and radius of inner sheath 8 of insulator.

Correspondingly, if N represents the location of the Nth resistance series - the pleat - then [(U * ln (r0) - In (r0 / n) * VN) / U] 15 rN = e.

The above modeling gives an optimum path but ignores the constraints imposed by the shape of the insulator or other similar component.

The plurality of plurality of plurality of plurality of plurality of plurality of resistor chains 6 are preferably separated by a plurality of parallel pleates. 2 mm insulation such as casting resin. The required insulation strength between the pleats depends on the magnitude of the voltage drop across the pleated resistors. When casting a voltage transducer in connection with an insulator, there is a resistor chain 6 advantageously:: * ·: 25 supported on the chain by an insulating rigid support structure 7. The support structure may: T: typically be plastic or cast resin. The support structure 7 for the resistor chain 6 provides the desired spiral path. Advantageously, the support structure may be shaped such that a support surface is also provided between the two parallel supported pleats. · ♦ ·. sufficient creep distance to improve the tension strength of the structure and * ♦ II! 30 reduces breakthrough sensitivity.

*: ** As shown in Figure 2, the longitudinal axis of the resistor elements 5 of the resistor chain 6 is parallel to the primary current conductor 2. In this case, there is no potential difference caused by a magnetic field between the ends ·: · * of the resistor element, i.e. in the individual. the so-called Rogowski phenomenon does not occur in the resistors because the magnetic field 2 of the primary current conductor 2 does not pass through the resistance loops of the resistor material 5 in the resistor elements 5.

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According to Figure 2, the upper resistor of the resistor chain 6 forming the voltage sensor is connected to the primary current conductor 2 by an electrode 3. The lower resistor of the resistor chain 6 is connected to the ground potential by another electrode 4. In addition, a third electrode is connected between the upper and lower resistors, from which the voltage measurement signal 5 is obtained by measuring between this electrode and the electrode 4 fixed to the ground potential. In order to minimize the effect of stray capacitances from the resistor circuit 6 constituting the voltage divider to the ground and the primary current conductor 2, and thus to minimize the phase error of the divider, the electrodes can advantageously be designed to act as electric field controllers. In this case, the shape 10 of the electrodes 3 may, for example, be U-shaped.

If it is advantageous for the sensor fitting - in connection with the support insulator or the like - the resistor chain 6 can also be shaped so that it proceeds in the screw thread direction in the direction of the primary current conductor 2.

Although the invention has been described above with reference only to an exemplary embodiment of a voltage sensor adapted to a support insulator, it is clear that the invention is not limited thereto, but can be modified in many ways within the inventive concept of the appended claims.

In addition, the following embodiments of the invention described above may be mentioned. The resistive voltage sensor for insulating structures of the invention may be constructed as a single moldable module, including an inner sleeve, an outer sleeve, a resistor chain and a resistor chain support structure and the necessary connections. Of course, the resistive voltage transducer according to the invention can be used in non-auxiliary insulator constructions, such as in-line insulators or in a mold-shaped structure.

The resistive voltage transducer according to the invention is intended to be disposed mainly in molded solid insulators, but it is also suitable for air or gas insulated structures at different voltage levels.

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Claims (14)

A resistive voltage sensor, particularly for use in medium and / or high voltage measurements and arranged in a space (1) comprising 5 insulating media, pierced by a primary current conductor (2), for example in connection with some type of insulator, comprising a voltage divider , that the upper and lower resistor of the voltage divider comprises a resistor chain (6) arranged around the primary current conductor (2) in a space (1) comprising an insulating medium in a substantially helical form. Voltage sensor according to Claim 1, characterized in that the resistively distributed potential of each point of the resistor chain (6) is substantially equal to the capacitively distributed potential 15 of the corresponding point of the electric field acting in the space (1) comprising the insulating medium. Voltage sensor according to claim 1 or 2, characterized in that the resistor chain (6) comprises one or more separate series-connected resistor elements (5). Voltage sensor according to claim 1, 2 or 3, characterized in that the resistor elements (5) of the resistor chain (6) are low-voltage resistors. Voltage sensor according to Claim 1, 2, 3 or 4, characterized in that the resistor elements (5) of the resistor chain (6) are surface-mount resistors. Voltage sensor according to one of the preceding claims, characterized in that the resistor elements (5) of the resistor chain (6) are arranged substantially parallel to the primary current conductor (2). Voltage sensor according to any one of the preceding claims, characterized in that the resistor elements (5) of the resistor chain (6) are arranged in a series of resistor elements (10) comprising 30 or more consecutive resistor elements (5) which: is substantially parallel to each other and to the primary current conductor (2) ·: ··:. . Voltage sensor according to Claim 7, characterized in that between the sets of resistors (10) consisting of separate resistor elements (5) there is at least 2 millimeters of insulating material, such as a casting resin. 106226 11 Voltage sensor according to claim 7, characterized in that the resistor sets (10) consisting of separate resistor elements (5), viewed from the transverse direction of the primary current conductor (2), are supported by a spiral support structure (7) made of insulating material around the primary current conductor (2). Voltage sensor according to one of the preceding claims, characterized in that the inner surface (8) of the resistor chain (6) and / or the helical support structure (7) supporting it against the inner surface (8) and the ground potential surface (9) The distance of 10 - the creep distance - is significantly longer than the radius between the surface (8) resting against the primary current conductor (2) and the surface (9) of the body. 10 106226 Voltage sensor according to Claim 9, characterized in that the helical support structure (7) supporting the resistor chain (6) is shaped such that the distance - creep distance - between two parallel resistor sets (10) along the surface of the support structure is substantially two parallel resistor elements (5). ). Voltage sensor according to one of the preceding claims, characterized in that the helical resistor chain 20 (6) forming the voltage divider is arranged in a thread extending in the direction of the primary current conductor (2) ... around the primary current conductor (2). Voltage sensor according to one of the preceding claims, characterized in that a:: capacitive component is coupled in parallel with the lower resistor of the voltage divider. "* ·: 25 Voltage sensor according to any one of the preceding claims, characterized in that the sensor electrodes (3,4) are configured to act as electric field controllers. · • • * * * t t t t t t t t t t t t t t | | | | | | | | | | | | | | | | | | | | | | | | | |. a «« 12 106226