Current accuracy class. Sensor principles

Transcription

1 Indoor Combi Sensor 12, 17.5 and 25 kv 1250 A and 3200 A KEVCD Highest voltage for equipment kv Rated continuous primary current A Rated transformation ratio for current measurement, K ra Rated transformation ratio for voltage measurement, K n Current accuracy class A /150mV (180mV) at 50 Hz (60 Hz) : 1 Class 1 (3) with (without) a correction factor Voltage accuracy class Class 1/3P Sensor principles Sensors feature a new solution for the measurement of currents and voltages needed for the protection and monitoring in medium voltage power systems. Sensors based on alternative principles have been introduced as successors to conventional inductive instrument transformers in order to obtain size reduction, performance improvement and better standardization. These principles are known since already a long time, but not until the introduction of versatile electronic relays it has been possible to make use of the advantageous properties of sensors designed on these principles. INDOOR Current sensor The measurement of currents by KEVCD sensors is based on the Rogowski coil principle. The Rogowski coil is a toroidal coil without iron core, placed around the primary conductor in the same way as as the secondary winding of a current transformer. The difference from the latter, however, is that output signal from a Rogowski coil is not a current, but a voltage: In all cases, a signal reproducing the actual primary current waveform is obtained by integrating the transmitted voltage signal. Current sensor I p U out

2 Voltage sensor The measurement of voltages in the KEVCD sensors is based on the principle of a resistive voltage divider. The output voltage is directly proportional to the input voltage: Voltage sensor R 1 In all cases, the transmitted signal reproduces the actual waveform of the primary voltage. U p R 2 U out Programmable protective and control IEDs (Intelligent Electronic Devices) The protective and control IED includes the functionality of both the conventional relays but also a lot of auxiliary functions. Even during a failure state the information transmitted from the sensors into the IEDs corresponds truly to the measured signal, hence guaranteeing the accuracy and giving the possibility for a versatile relay function. The IED, however, has to be able to operate at sensor s low input signal level with sufficient accuracy, and the signal from the Rogowski coil must to pass through a process of integration. Contemporary IEDs (e.g. the ABB feeder terminals of the RE series) are already designed for the use of sensors, and they are also equipped with built-in integrators at the inputs of Rogowski coil sensor. Noticeable differences between sensors and instrument transformers From the practical point of view there exist two noticeable differences between sensors and the conventional induction-based instrument transformers: INDOOR Linearity Due to the absence of ferromagnetic core the magnetic circuit cannot become saturated and, consequently, the sensors are linear up to the highest currents and voltages. On a practical level two significant advantages have been achieved: ε Accuracy limits Rated current Current sensor I p (log) Current transformer 2 1. The measurement and protective function can be realized with one single secondary winding with double ratings (for measurement and protection) 2. Only one single standard sensor can be used for a range of switchgear rated currents and voltages. Compactness As sensing elements are noticeably smaller and the same elements can be used for both the measurement and protective purposes, the current and voltage sensors can easily be combined in one device, the Combi Sensor, still smaller than a conventional current transformer. In principle the KEVCD sensor is a combined sensor with the possibility to be delivered without the voltage-sensing element.

3 Advantages of this sensor technology New IED technology Rated range Example: Rated current range: 80 to 1250 A, accuracy class 1. The accuracy class limits correspond to those in the figure. ε +3 % +1 % -1 % -3 % 0.05x80 A = 4 A Accuracy limits Typical accuracy Rated current range 80 A 1250 A I p (log) 1.2x1250 A = 1500 A Since the voltage and current sensors are highly linear within a very broad range of voltages and currents, respectively, one and the same sensor can be used for various rated voltages and currents of a switchgear. Instead of one value of rated current, a current range is defined for the sensor. For every switchgear rated current within the rated current range of sensor the engineering parameters of the sensor, specified by a standard, are met for the particular rated current. To achieve correct functioning of the protection and control IEDs the chosen rated current as well as the rated transformation ratio must be programmed to the IED. The same applies also for the rated voltage range for voltage sensors. Correction factor The amplitude error of a current sensor remains to be virtually constant and does not depend on the primary current. Hence, it can be corrected in the IED by using a correction factor measured separately for every sensor during the routine testing. A sensor fulfilling the requirements of e.g. class 3 without the correction factor can be rectified by software in a way to meet the requirements of class 1 with the use of the correction factor. For voltage sensors correction factors are not used. Adapter If the transmitted signal from the current sensor is too high to be processed properly by the IED, an adapter is to be inserted between the sensor cable and the IED adapter unit. Simply said, the adapter operates as a highly accurate voltage divider giving a higher transformation ratio of the current sensor. The adapters have to be matched to the actually used IED and must be ordered in combination with the sensor. Cable The kind and length of cable has a considerable impact on the total accuracy of the sensor. Therefore, the accuracy of every sensor is to be tested jointly with the cable specified in the purchase order. Even if the cable may be disconnected from the sensor for the purpose of transport and mounting, the accuracy class specified is valid only when the sensor is equipped with its original cable having the same production number as the sensor itself. The cable is available in three standard lengths, with the length to be specified in the purchase order. 3

4 Standards KEVCD sensors are designed, manufactured and tested in accordance with the latest international standards to apply at areas for which the sensors can be used. INDOOR Dimensions: DIN 42600, part 8 (narrow design) Voltage sensors: IEC ( ) Instrument transformers - Part 7: Electronic voltage transformers Current sensors: IEC ( ) Instrument transformers Part 8: Electronic current transformers Combi Sensors: IEC ( ) Instrument transformers Part 3: Combined transformers 4

5 Technical specifications of Combi Sensors type KEVCD Description Supporting type Combi Sensor consisting of the following: - Rogowski coil current sensor... all versions - resistive divider type voltage sensor... versions AE and BE - coupling electrodes for voltage detection systems (VDS) or voltage presence indication systems (VPIS)...all versions - interconnecting cable Available types Rated primary currents: A Rated primary currents A Remarks KEVCD 12 AE3 AG3 KEVCD 12 BE2 BG2 KEVCD 12 AE3C AG3C KEVCD 12 BE2C BG2C increased insulation level KEVCD 17.5 AE3 AG3 KEVCD 17.5 BE2 BG2 KEVCD 24 AE3 AG3 KEVCD 24 BE2 BG2 Versions Functions included Voltage sensor Current sensor Coupling electrode for VDS and VPIS KEVCD AE_, -BE_ KEVCD AG_, -BG_ Dimensions and primary terminal arrangement The dimensions and the arrangement of primary terminals comply with the stipulations of the DIN standard, part 8 (narrow design). On request reversed polarity on the primary side. Highest voltage for equipment and test voltages Highest voltage for equipment U m /kv Power frequency test voltage kv Lightning impulse test voltage kv KEVCD 12_ KEVCD 12_C KEVCD 17,5_ KEVCD 24_ Temperature categories operation: -5/40 C storage and transport: -40/70 C 5

6 Voltage sensors, rated values Overvoltage factor k u : 1.9/8 hours DC withstand voltage: 70 kv/30 min. Rated frequency f n : 50/60 Hz Rated accuracy: class 1/3P Rated burden: 4 10 MΩ Rated primary voltage range and rated transformation ratio: KEVCD 12_E_ KEVCD 17.5_E_ KEVCD 24_E_ Rated primary voltage range U pn /kv 6: 3-11: 3 6: 3-15: 3 6: 3-22: 3 Rated transformation ratio K n : : :1 Current sensors, rated values Rated frequency f r : 50/60 Hz Rated accuracy: class 1 (class 3 without the use of correction factor) Rated burden: 4 10 MΩ Rated continuous thermal current, short-time thermal current and dynamic current: Typ Rated continuous thermal current I cth /A Rated short-time thermal current I th /ka, 3 sec. Rated dynamic current I dyn /ka KEVCD 12 A_ KEVCD 17.5 A_ KEVCD 24 A_ INDOOR KEVCD 12 B_ KEVCD 17.5 B_ KEVCD 24 B_ KEVCD 12 A_ KEVCD 17.5 A_ KEVCD 24 A_ KEVCD 12 B_ KEVCD 17.5 B_ KEVCD 24 B_ Rated primary current range and rated transformation ratio: Rated primary current range I pr /A Rated transformation ratio K ra 80 A/0.150 V at 50 Hz 80 A/0.180 V at 60 Hz 1600 A/0.150 V at 50 Hz 1600 A/0.180 V at 60 Hz

7 Adapters for protection and control IEDs Adapters for protection and control IED units from ABB are to be selected from the table below. Note that both rated current of switchgear and the linearity limit for the chosen combination of sensor and IED is to be considered. IED types: REX, REF 54_, REM Switchgear rated current I r /A Sensor to be used Adapter to be used Linearity limit for the combination chosen (highest rms value) Resulting transformation ratio at 50 Hz (60 Hz) K ra KEVCD _ A_ KEVCD _ A_ KEVCD _ A_ No adapter needed 1VL R0101 1VL R A A A 80 A/0.150 V (0.180V) 240 A/0.150 V (0.180V) 640 A/0.150 V (0.180V) KEVCD _ B_ No adapter needed > A 1600 A/0.150 V (0.180 V) Cable Standard cable lengths: 5.0; 6.5 and 7.5 m Cable connector type: Twin BNC Coupling electrode for voltage detection systems Intended to be used in: - voltage detection systems (VDS) according to IEC voltage presence indication systems (VPIS) according to IEC If there is no connection of the coupling electrode to the coupling system the electrode must be earthed. Capacitance values: C1 = pf C2 25 pf KEVCD 12 a 17.5 C1 = pf C2 25 pf KEVCD 24 Ordering data Arrangement Cable length Adapter (if needed) Special design (on request) - reversed polarity on primary side 7

8 Dimensions and weights KEVCD 12A-3 KEVCD 12A-3C KEVCD 17,5A-3 Weight: 12 kg KEVCD 24A-3 INDOOR Weight: 16 kg 8

9 KEVCD 12B-2 KEVCD 12B-2C KEVCD 17,5B-2 Weight: 23 kg KEVCD 24B-2 Weight: 26 kg 9

10 INDOOR ABB s.r.o. Vídeňská 117 Tel.: Brno, Czech Republic Fax: The technical data and dimensions are valid as of the time of publishing. We reserve the right to subsequent alterations and modifications. 1VLC Rev.3, en