TECHNICAL FIELD OF THE INVENTION

The technical solution refers to a combined measuring and detecting system on an electric conductor including at least one sensor of electric current having a shape of a ring around the electric conductor and/or at least one sensor of electric voltage having a shape of a ring around the electric conductor.

PRIOR ART

Construction of measuring transformers or any other detecting elements is usually designed so that it may suit to a given solution. In case that the measuring

transformer is designed for one application, it is capable of meeting limiting values of a withstand voltage for this application. In case that the same transformer is used for other applications, the withstand voltage value may not any longer meet appropriate requirements and therefore it may be difficult to use such a measuring transformer on given unfavourable conditions. In addition electric fields from surroundings can have an influence on measured values and in such way to influence measurement accuracy.

As currently a construction of measuring transformers is designed for a specified application, it is necessary, provided that the measuring transformer is to be used for a different application, to perform dielectric tests to find out whether dielectric resistance of the whole assembly is sufficient. If it is found out that it is not the case, it is necessary to design external apparatuses, special arrangement or additional insulation in order to reach a sufficient dielectric resistance of the whole assembly. Various solutions for the same measuring transformer in various applications can be necessary to meet the same requirements.

SUMMARY OF THE INVENTION

The above shortcomings of the state of the art are eliminated to a great extent by a combined measuring and detecting system on a primary conductor including at least one sensor of electric current having a shape of a ring around the primary conductor and/or at least one sensor of electric voltage having a shape of a ring around the primary conductor. The substance of the technical solution is that a space between the electric current sensor and/or the electric voltage sensor and the primary conductor is at least from one side separated from surrounding area by a conductive electrode having a shape of a ring around the primary conductor.

In an advantageous embodiment this combined measuring and detecting system includes both the electric current sensor and the electric voltage sensor. The ring of the conductive electrode has an inner circular edge and an outer circular edge, and the conductive electrode surface between the inner and the outer circular edges forms an angle ranging from 60° to 120° with an axis of the primary conductor. The conductive electrode is adjacent by its inner circular edge to the primary conductor and is conductively connected to it, and its outer circular edge is farther from the primary conductor surface than the inner side of the electric current sensor. The electric voltage sensor is arranged between the primary conductor and the electric current sensor in order to shield the electric voltage sensor from external influences. The conductive electrode at its outer circular edge is bent in the direction outwards from the electric current and electric voltage sensors or rolled into a hem having a circular cross-section.

Also in another advantageous embodiment the combined measuring and detecting system includes both the electric current sensor and the electric voltage sensor. The same way as in the preceding embodiment the ring of the conductive electrode has an inner circular edge and an outer circular edge, and the conductive electrode surface between the inner and the outer circular edges forms an angle ranging from 60° to 120° with an axis of the primary conductor. However the conductive electrode is attached by its outer circular edge to the electric current sensor and is earthed and the electric voltage sensor is arranged between the primary conductor and the electric current sensor in order to shield the electric voltage sensor from external influences. The conductive electrode at its inner circular edge in a distance from the primary conductor surface is bent in the direction towards the electric current and electric voltage sensors or rolled into a hem having a circular cross-section.

Also another advantageous embodiment of the combined measuring and detecting system includes both the electric current sensor and the electric voltage sensor. It is likewise true that the ring of the conductive electrode has the inner circular edge and the outer circular edge, and the conductive electrode surface between the inner and the outer circular edges forms an angle ranging from 60° to 120° with the axis of the primary conductor. However the conductive electrode is on a floating potential and the electric voltage sensor is arranged between the primary conductor and the electric current meter in order to shield the electric voltage sensor from external influences. Also in this case the conductive electrode at its inner circular edge in a distance from the primary conductor surface is bent in the direction to the electric current and electric voltage sensors or rolled into a hem having a circular cross- section.

In a particularly advantageous embodiment the conductive electrodes in the combined measuring and detecting system are arranged at both sides of the area between the electric current and the electric voltage sensors and the primary conductor.

In another advantageous embodiment the electric current sensor is implemented as a current transformer or as a low-performance current sensor.

In this or in another advantageous exemplary embodiment the electric voltage sensor is implemented as a capacitance divider and/or a resistor divider.

In case the conductive electrode is bent at its inner circular edge or is rolled into a hem having a circular cross-section the curvature radius of the bent or rolled end of the conductive electrode is greater than 1 mm.

In case that the conductive electrode is not connected conductively to the primary conductor, in an advantageous embodiment of the technical solution the inner radius of the conductive electrode ring is smaller than the distance of the ring-shaped voltage sensor from the axis of the primary conductor.

In such a case it is also advantageous if the electric voltage and electric current sensors assembly with the conductive electrodes are embedded in an insulating material, whereas the distance of the electric voltage and electric current sensors as well as the conductive electrodes from the insulating material surface is greater than 1 mm.

And finally in another advantageous embodiment of the technical solution the combined measuring and detecting system includes a temperature sensor in addition to the electric current sensor or electric voltage sensor. BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution will be described in details hereinafter with reference to the accompanying drawings wherein:

Fig. 1 is a partial cross-section of the combined measuring and detecting system with the conductive electrode connected conductively to the primary conductor, and Fig. 2 is a partial cross-section of the combined measuring and detecting system with the conductive electrode connected to the electric current sensor.

DETAILED DESCRIPTION OF THE DRAWINGS

The first exemplary embodiment of the combined measuring and detecting system 1 on the primary conductor 3 is depicted in Fig. 1. This combined measuring and detecting system 1 includes the electric current sensor 2 in the shape of the ring around the primary conductor 3 and the electric voltage sensor 6 in the shape of the ring around the primary conductor 3. Two conductive electrodes 4 in the shape of the ring around the primary conductor 3 are connected conductively to the primary conductor 3, the conductive electrodes 4 separating the space between the electric current sensor 2 and the electric voltage sensor 6 from surrounding area. Specific resistance of the conductive electrodes 4 material can tend to zero but it can reach up to tens or hundreds of kQ.

The ring of the conductive electrode 4 has the inner circular edge 7 and the outer circular edge 8 and the area of the conductive electrode 4 between the inner and the outer circular edges 7 and 8 forms an angle of 90° with the axis 9 of the primary conductor 3. The conductive electrode 4 can incline even at another angle, i. g. angle ranging between 60° to 120°, and thus create a lateral area of a truncated cone if it meets the requirement to shield the electric voltage sensor 6 from perturbative influences, especially from the direction parallel with the axis 9 of the primary conductor 3. Owing to easy assembling it is better if the surface of the conductive electrode 4 is perpendicular to the axis 9 of the primary conductor 3. The conductive electrode 4 is adjacent by its inner circular edge 7 to the primary conductor 3 and is conductively connected to it, and the outer circular edge 8 of the conductive electrode 4 is farther from the primary conductor 3 surface than the inner side of the sensor 2 of electric current. The electric voltage sensor 6 is arranged between the primary conductor 3 and the electric current sensor 2 in order to shield the electric voltage sensor 2 from external influences. At that the conductive electrode 4 is bent at its outer circular edge 8 in the direction from the electric current and electric voltage sensors 2 and 6, respectively. However the conductive electrode 4 at its outer circular edge 8 can be rolled into a hem of a circular cross-section so that the arrangement is created in which the possibility of dielectric discharges from the outer circular edge 8 of the conductive electrode 4 is minimised. In an exemplary embodiment both the bending and the rolling of the conductive electrode 4 at its outer circular edge 8 have a radius R of a curvature greater than 1 mm.

The electric voltage sensor 6 is arranged between the electric current sensor 2 and the primary conductor 3 so that it is shielded from perturbative influences from outside by the ring-shaped electric current sensor 2. Besides it is shielded even by the conductive electrodes 4 from both sides in the direction parallel to the axis 9 of the primary conductor 3. The outer radius B of the ring-shaped conductive electrode 4 is greater than the inner radius A of the ring-shaped electric current sensor 2. The complete combined measuring and detecting system 1 is imbedded in a block 10 of an insulating material 5, at best of a permitivity greater than , whereas both the distance D of the electric current sensor 2 from the block 10 surface and the distance E of the conductive electrode 4 from the block 10 surface are greater than 1 mm. Also the radius S of the electric voltage sensor 6 is greater than 1 mm.

The second exemplary embodiment of the combined measuring and detecting system 1 on the primary conductor 3 is depicted in Fig. 2. This embodiment differs from the first one in that the conductive electrodes 4 are connected to the electric current sensor 2 and thus they are not on the voltage of the primary conductor 3. The conductive electrodes 4 can be either earthed together with the electric current sensor 2 or they can be on another or floating voltage together with the electric current sensor 2. The conductive electrodes 4 are ring-shaped and have the bent or rolled part on their inner edges, which are at a distance C from the primary conductor 3 surface. In this embodiment the electric voltage sensor 6 is arranged between the electric current sensor 2 and the primary conductor 3 so that it is shielded from perturbative influences from outside by the ring-shaped electric current sensor 2. In the same way it is also shielded from both sides in the direction parallel to the axis 9 of the primary conductor 3 by the conductive electrodes 4. In the same way as in the previous embodiment also in this case the complete combined measuring and detecting system 1 is imbedded in the block 10 of the insulating material 5, whereas both the distance D of the electric current sensor 2 from the block 0 surface and the distance E of the conductive electrode 4 from the block 10 surface are greater than 1 mm. Even in this case the radius S of the electric voltage sensor 6 is greater than 1 mm.

In operation the combined measuring and detecting system 1 arranged on the primary conductor 3 measures voltage and current of this primary conductor 3. The conductive electrodes 4 keep a constant voltage, namely either a voltage identical with the voltage on the primary conductor 3 as in the first exemplary embodiment, or a zero voltage or floating voltage as in the second exemplary embodiment, what causes a favourable behaviour of electric field between them. The electric voltage sensor 6, which is arranged between them, is thus in a homogenous electric field that is not influenced by the shielded external influences, all the more so, that the electric voltage sensor 6 is shielded from the side perpendicular to the axis 9 of the primary conductor 3 by the electric current sensor 2. The voltage measuring is stabilized by this arrangement and is not subject to accidental deviations and interferences caused by various applications, which increases its accuracy, reliability and applicability.

INDUSTRIAL APPLICABILITY

The combined measuring and detecting system according to the technical solution can be advantageously used for measuring of electric current and voltage in heavy current electrical engineering, e.g. for switchboards.