EP1592974A2

EP1592974A2 - Measuring system comprising an intelligent sensor head and having a reduced power consumption for medium-voltage or high-voltage systems or in mining, and method therefor

Info

Publication number: EP1592974A2
Application number: EP04710364A
Authority: EP
Inventors: Hermann Hampel
Original assignee: IAD Gesellschaft fuer Informatik Automatisierung und Datenverarbeitung mbH
Current assignee: IAD Gesellschaft fuer Informatik Automatisierung und Datenverarbeitung mbH
Priority date: 2003-02-12
Filing date: 2004-02-12
Publication date: 2005-11-09
Also published as: DE10305986B4; WO2004072662A2; DE10305986A1; WO2004072662A3; CN1761881A; CN100422749C; US7869707B2; US20060291856A1

Abstract

The invention relates to a measuring system comprising an intelligent sensor head and having a reduced power consumption for medium-voltage or high-voltage systems or in mining, and to a method therefor. Differently designed measuring systems exist of which most contain a central signal processing unit and a number of electrical measuring components, and in which the measured values furnished by the measuring components are optically transmitted over optical waveguides. The aim of the invention is to provide a measuring system of this type, which has a low power consumption and enables a reliable optical data transmission. To this end, an optical loop is provided between a central measuring unit (MG) and a sensor head (SK). Microprocessors (MP1, MP2), which are situated inside the central measuring unit (MG) and inside the sensor head (SK), carry out transmitting, measuring and monitoring tasks as a distributed controller with bidirectional data communication. A frame synchronization signal serves both for supplying power as well as for deriving a clock signal for block-oriented data transmission. A data communication is carried out for conducting a parameterization and/or programming between the central measuring unit (MG) and the sensor head (SK), and a pre-preprocessing of the measured values is carried out in the sensor head (SK), particularly a measured value correction and/or a range switching and/or a reprogramming of the filtering characteristics and/or an automatic compensation are/is carried out in the sensor head (SK). The invention is used in measuring systems, particularly those having optical signal and power transmission.

Description

"Measuring system with intelligent sensor head and reduced energy consumption for medium or high voltage systems or in mining and methods for this"

description

The invention relates primarily to a measuring system for medium or high voltage systems or in mining with optical signal and energy transmission between a sensor head and a central measuring device (claim 1). The invention further relates to a method for this (claim 12). '

Voltage transformers are generally used to measure the operating voltage in medium or high-voltage switchgear. The insulation and the turn ratio must be selected according to the operating voltage of the switchgear in order to reduce the operating voltage to an internal voltage of less than 100 V suitable for measurement purposes. Depending on the task (billing measurement, line and device protection technology, operational measurement technology), single-pole or double-pole insulated voltage transformers in various designs are used.

Voltage converters generally have a high share of the costs of switchgear panels and switchgear measurement technology. They have large dimensions and influence the construction of the switchgear. She . are sensitive to overvoltages and are the weakest link in switchgear engineering in terms of device technology. Secondary connecting cables between voltage transformers and protective relays or between voltage transformers and

Measuring devices can be strongly influenced by magnetic fields, earth leakage currents, short-circuit currents and interference fields, which in many cases falsifies the measurement result. From DE 37 27 950 C2 a device for carrying out voltage measurements in medium or high voltage switchgear is known, which offers a complete replacement for the use of voltage transformers in the context of operational measurement technology. The opto-electronic sensors used there enable electrical and mechanical decoupling between the measuring point and the display, are insensitive to interference fields and overvoltages, and are also characterized by small dimensions and relatively low costs. To carry out voltage measurements in the form of a phase comparison measurement, two optoelectronic sensors connected to the part supporter with a coupling electrode are provided. Furthermore, two optoelectronic sensors in a ferroelectric design are provided, which are connected via fiber optics to a remotely located transceiver and are simultaneously scanned by these transceivers using the reflection method. A phase comparison device is connected to the two transceivers, two comparators connected to the two transceivers converting the supplied analog input signal into a square-wave signal. Two monostable multivibrators connected to the comparators generate synchronous short pulses from the square wave signals with the zero crossings of the two phases. Finally, a totalizer connected to the output of the two multivibrators is provided, which counts incoming pulses as a single pulse, incoming pulses, however, counts as separate pulses, and devices for evaluating and displaying phase equality, phase opposition, and lack of one are connected to the outputs of the totalizer Phase disturbance and operability connected. In an alternative embodiment, a series circuit with a diode and a further capacitance is arranged parallel to the capacitor arranged between the coupling electrode and ground, and a voltage-dependent CMOS pulse generator is connected in parallel therewith. To the outputs of the pulse generator is connected the capacitor in the ferroelectric design opto-electronic sensor, which via the Optical fiber is connected to a light transmitter-receiver with measuring amplifier. The measuring amplifier contains an element designed as a digital-analog converter or frequency-voltage converter for converting the pulse frequency into a value suitable for the input of a voltage measuring device. In the device according to DE 37 27 950 C2, the signal processing and evaluation takes place remotely from the measurement location, namely centrally.

A monitoring device for protection against mast damage is known from DE 38 24 000 C2, in which other sensors can be used in addition to fiber optic sensors. In particular, an optical waveguide, an infrared detector or a structure-borne sound microphone is used as a sensor on each mast foot and an optical waveguide line is routed from it to the monitoring device. With the fiber optic sensor, a stripped fiber optic cable in the form of a loop is guided along a corner post base of the mast, and it merges into a double-core jacketed fiber optic cable at the upper end of the monitoring area. This line is continued along a mast corner post to a central monitoring device, which is arranged in a metal housing in the upper third of the mast on a mast traverse. In addition to the central monitoring device, there is a single monitoring device for each infrared detector and structure-borne sound microphone, which is designed as an electronic module in a metal housing and is arranged at the upper end of the monitoring area in a corner post of the mast. From there, a single-core fiber optic cable is led to the central monitoring device. While infrared detectors or structure-borne sound microphones are built into the signal device, only the cable of the fiber optic sensor is inserted into the signal device. The optical signals emitted by the individual devices are converted in the central device and fed to the evaluation logic which, in cooperation with the sequence control, translates the alarm message via a radio data link to the control room. A distinction can be made there from which signal devices triggered the message

/ has been. The signaling devices with infrared detector or structure-borne sound microphone have a battery supply and the following components connected in series: sensor, amplifier, Filters, evaluation logic. Light-emitting diode and socket for the connector of the fiber optic cable to the central device. An HP infrared filter is used for a passive infrared detector to suppress unwanted temperature outputs, while an active BP filter is used for frequency selection for a structure-borne sound microphone. The evaluation logic decides whether it is an alarm or not. In the monitoring device according to DE 38 24 000 C2, signal preprocessing and evaluation take place at the measuring location.

A combined current and voltage converter for outdoor switchgear with a semi-conventional voltage converter in the form of a CC, RR or RC divider and a purely optical current converter in the form of an optical fiber loop surrounding the high voltage conductor is known from DE 198 32 707 C2. Furthermore, a common transformer evaluation device, which is at ground potential, is provided for the current transformer and the voltage transformer. In this way, the measured variables of the individual phases can be assigned to one another when evaluating the signals from the voltage converter part and the current converter part, and a phase-synchronous measurement of the individual phases can take place.

Furthermore, DE 195 43 363 C2 describes a measuring transducer arrangement for measuring currents or voltages in medium or high voltage systems, with at least one current or voltage sensor for recording the measured values, with at least one encoder for coding the measured values, with at least one light transmitter for

Send and at least one light receiver to receive the coded

Measured values, and known with at least one decoder for decoding the measured values at the receiving location. To the transducer arrangement in a simple manner

To install a medium or high voltage system and adapt it to the respective measurement requirements without great effort, the measuring transducer arrangement is composed of mutually combinable modules with standardized interfaces. Furthermore, at least one sensor module with the current or voltage sensor, at least one transmitter module with the encoder and the Light transmitter and at least one receiver module provided with the light receiver and the decoder. The dimensions and connections of the sensor module and transmitter module are matched to one another and mechanically combined to form a high-voltage assembly, which as a unit ensures simple installation in the high-voltage system. In a preferred embodiment, the sensor module for measuring DC or AC voltages has a voltage sensor in the form of a preferably frequency-compensated ohmic divider, which is provided on the low-voltage side with an overvoltage arrester. As a coder, the transmitter module can have a voltage-frequency converter for generating a pulsed carrier signal and a light transmitter with at least one transmitter diode for converting the carrier signal into light pulses. The receiver module accordingly has a light receiver with a light-sensitive receiving diode for converting light pulses into an electrical pulsed carrier signal and as a decoder a frequency-voltage converter. The transmitter module and receiver module are optically connected to one another by an optical waveguide. Furthermore, the high-voltage assembly has an auxiliary power supply unit for supplying the transmitter module, the auxiliary power supply unit being fed via optical fibers.

Furthermore, DE 100 10 913 Cl describes a device for monitoring the

Gas density of an insulating gas-filled high-voltage transmission line, which is divided into a plurality of line sections by bulkheads, is known, which is in the area of

Contains components arranged for measuring the gas density in the line sections and for sending measurement results and a signal processing unit for receiving and evaluating the measurement results. In particular, it is provided that the measuring components are fed from a centrally arranged energy source containing a light source via at least one energy supply line designed as an optical waveguide, the measuring components opto-electrical energy converters for converting light into contain electrical energy, and several measuring components are serially connected to the light source via a common power supply line. The power supply line and the signal transmission line can also be combined in the form of a simple optical waveguide. The measuring component essentially consists of an energy processing unit, a computing unit and a sensor unit. The

Energy processing unit is supplied with energy from an energy source containing a light source via an energy supply line designed as an optical waveguide and an opto-electrical energy converter. Depending on the configuration of the monitoring device, the light source contains one or more laser diode modules, each with up to 500 mW of power. Furthermore, the energy processing unit contains a capacitor, for example a low leakage current ELKO or an array of tantalum or ceramic capacitors, which stores the energy emitted by the energy source and emits it to the computing unit if required. The computing unit, which essentially comprises a microprocessor, is used to control the sensor unit, to record and process the values measured by the sensor unit and to transmit the processed measured values via a light diode, a signal transmission line designed as an optical waveguide and a light sensor to the signal processing unit. In the associated method for monitoring the gas density of an insulating gas-filled one

High-voltage transmission line is provided that the measurement component is supplied with constant power from the energy source during a wait state, then the gas density is measured by the measurement component, the measurement value is transmitted to the signal processing unit, and then the measurement component is returned to the wait state until the next measurement. ,

Finally, a fiber-optic interface system is known from DE 695 20 371 T2, in which a control ensures that the current that is supplied to a laser light source is as low as permissible, so that a remote interface and a process variable transmitter still have sufficient energy at the same time provided. In particular, a first, locally stationed microcontroller device is provided, which serves for the controllable supply of light energy at a first output connection and for receiving digitally coded, optically transmitted information of the remote location at a first input connection of the microcontroller device. An analog transmission device is electrically connected to the first, locally stationed microcontroller device and is set up in such a way that either analog or digital information or both are simultaneously transmitted to a local control system. A second microcontroller is stationed at a remote location, ie remote from the first microcontroller, and is used to receive analog and / or digital signals which define the state of a process variable, such as pressure, temperature, flow, movement, density or other parameters, which was detected by a remote process variable transmitter, and for delivering optically coded status information to a second output connection. There is one to the second microcontroller and the remote process variable transmitter

, Coupled energy supply device that supplies them with electrical energy.

The energy supply device contains an optical-to-electrical

Energy converter with a second input connection. Between, the first

The output connection of the locally stationed equipment and the second input connection of the remotely stationed optical-to-electrical energy converter are connected to at least one optical fiber. The same or a second optical

- Fiber is stationed between the second output port

Microcontroller and the first input connection of the first, locally stationed microcontroller. Furthermore, a device including the first microcontroller initially feeds light energy at an eye safe low level to the first output port. The second microcontroller responds to the reception of the eye-safe low light energy value ^• via the first optical fiber and sends a start-up command via the optical fiber connection to the first, locally stationed microcontroller, whereby the first optical fiber has additional ones Light energy above the eye safe lower value is only supplied if it is properly connected between the corresponding output and input connections. Furthermore, there is a light source energy supply device at the local location which supplies a light source, such as a gas laser, a laser diode or an LED, with electrical energy, the light source being a device for modulating the intensity of the light energy, which is provided to the first output connection , contains. The first microcontroller also contains a first microprocessor for controlling the light source energy supply device and the light source modulation device. The first microprocessor receives energy status information from the remotely located second microcontroller, so that regulation, in particular PI regulation (proportional integral regulation), of the optical energy, ie the laser current, is made available from the local location to the remote location is carried out in "quasi-static operation" while checking the laser voltage at regular intervals (status messages: message from six 8-bit bytes).

As the above assessment of the state of the art shows

I known differently designed measuring systems, which mostly contain a central signal processing unit and several electrical measuring components and in which the measured values supplied by the measuring components optically

Optical fibers are transmitted. However, because of such measuring systems a high one

Operational safety, for example when monitoring a

High-voltage circuit breaker is required, a secure measured value acquisition and reliable fiber optic data transmission is desirable. However, too little attention is paid to the fact that the permanent control of the laser diode for remote supply of the

Measuring components leads to a significant reduction in the life of the laser diode. In addition, because of the electromagnetic influences emanating from the high-voltage systems, in particular due to switching operations at a high voltage level, interference signals during optical signal transmission are a Can cause interference due to clock shift of the measuring signals (measuring currents or measuring voltage). The fiber-optic interface system according to DE 695 20 371 T2 with its "quasi-static operation" only ensures that the current that is supplied to the laser light source is as low as permissible. For this reason, in practice there is no fiber-optic measuring system which has low power consumption This is particularly important because the medium or high-voltage equipment manufacturing industry can be seen as an extremely progressive, development-friendly industry that quickly takes up improvements and simplifications and puts them into practice

Compared to the known measuring systems, the object of the invention is to provide such a measuring system which has low energy consumption and enables reliable optical data transmission.

This task is based on a measuring system for medium or

High voltage systems or in mining with optical signal and

Energy transmission between a sensor head with at least one sensor element and a central measuring device, solved by • providing in the central measuring device a light transmitter controlled by a microprocessor, which is used for data communication and for the energy supply of the

Emits a light superimposed on various components to a first optical waveguide,

• A light receiver connected to the first optical waveguide and a microprocessor are provided in the sensor head, the

Microprocessor after activation by the light receiver to control the

Sensor element, which is used to record and process the values measured by the sensor element and a data communication for transmitting the processed measured values to the central measuring device via a light transmitter second optical fiber and one arranged in the central measuring device

The light receiver controls such that the two microprocessors perform transmission, measurement and monitoring tasks as a distributed control with bidirectional data communication, a frame synchronization signal being used both for energy supply and for deriving a clock signal for block-oriented data transmission and / or a data communication for parameterization and / or or programming between the central measuring device and the sensor head as well as preprocessing of the measured values in the sensor head, in particular a measured value correction and / or a measuring range switchover and / or reprogramming of the filter characteristics and / or an automatic adjustment in the sensor head.

The measuring system according to the invention has the advantage that, due to the distributed control, faults in the measuring transducer system are immediately recognized and undesired consequences, for example a false alarm or a shutdown of the means or

High-voltage system or the monitored device can be avoided.

Furthermore, measurements with high resolution (for example from previously 12 bits to 16 bits) and a measuring range switchover can be carried out and a measurement value correction with regard to offset, gain, temperature or

Lifetime (aging) can be made. The automatic adjustment can be carried out both in manufacturing (thereby improved testing and manufacturing technology) and in

Operation. Furthermore, in the measuring system according to the invention, a combined energy-data transmission control is made possible, and the overall low power consumption and the dynamic operating mode mean that the service life of the light transmitter (laser diode) is greater than that of the appreciated one

State of the art, considerably increased.

_**

Furthermore, this object, according to claim 12, by a method for measuring currents or voltages in medium or high voltage systems and solved in mining with optical signal and energy transmission between a central measuring device and a sensor head with at least one sensor element, in which microprocessors arranged in the measuring device and in the sensor head carry out transmission, measurement and monitoring tasks as distributed control with bidirectional data communication, in which the measuring device Arranged microprocessor controls the energy transfer in dynamic operation in accordance with a frame synchronization signal in which, for preprocessing the measured values and / or for automatic adjustment in the sensor head, the reference voltage is measured in the climatic cabinet and stored in at least one microprocessor and in which the microprocessor arranged in the sensor head performs an adjustment process and carries out an error calculation and controls a DC-free and error-correcting data transmission.

The method according to the invention has the advantage that low energy consumption and reliable optical data transmission are made possible in a surprisingly simple manner, depending on the operating state between the two microprocessors as. distributed control with bidirectional data communication transfer parameters or data and the data / messages are monitored according to their data transmission quality and for timely arrival.

In a preferred embodiment of the invention, an analog-digital converter is provided in the sensor head, which is connected to the microprocessor, and the microprocessor corrects the digital supplied via the analog-digital converter. Measured value and / or supplemented by data with system information, segments the resulting data, encodes by means of block coding and provides this with information for segmentation in such a way that DC-free and error-correcting data transmission is possible; This embodiment of the invention has the advantages that overdriving of amplifiers provided during data transmission is reliably prevented (due to the absence of DC voltage) and that reliable data transmission can be established by adding redundancy at the transmitter and error correction at the receiver (due to the error correctability).

In a development of the invention, according to claim 3, the sensor head has a multiplexer, the inputs of which are each connected to sensor elements, the measurement channel being switched over by means of the microprocessor. This development of the invention has the advantage that further measurement signals can be fed to the microprocessor, so that, for example, an adjustment in the sensor head or phase comparison measurements (several sensor heads) can be carried out.

In a preferred embodiment of the invention, according to claim 4, an impedance converter for the tapped measurement value is connected to the output of the multiplexer and a differential amplifier is arranged between the output of the impedance converter and the input of the analog-digital converter, which is connected to the microprocessor for measuring range switching.

This embodiment of the invention has the advantage that the impedance converter generates a high-resistance input, the differential amplifier making it possible to adapt to the modulation limit of the analog-digital converter. Furthermore, the measuring range switchover allows the measuring system according to the invention to be used for several measuring ranges (a separate measuring system was previously required for each range).

Preferably, according to claim 5, the sensor element for the same or

AC voltage measurement an ohmic voltage divider and / or for current measurement an inductive current transformer with a downstream filter Transient and high-voltage pulse filtering and a protective element arranged serially to this.

The combination of filter and protective element reliably prevents the measurement from being falsified by transient and high-voltage pulses as well as the damage / destruction of the measuring system.

In a development of the invention, a temperature sensor is arranged in the sensor head, which is connected to one of the inputs of the multiplexer. is. Furthermore, according to claim 7, the sensor head has a reference voltage source and - for comparison - controlled by the microprocessor, the respective temperature-dependent reference voltage value can be supplied via an input of the multiplexer or a control input of the analog-digital converter.

This further development of the invention has the advantage that an adjustment with respect to temperature and aging, i.e. the calculation of the temperature response of the reference voltage and the temperature response and the aging of the components, for example the amplifier, is made possible.

According to claim 8, a filter connected to the light receiver is preferably arranged in the sensor head. the output of which the frame synchronization signal and / or the subsequent data signal can be tapped and fed to the microprocessor.

The filter enables the signals of interest to be filtered out (frame synchronization / data) or the removal of higher-frequency interference signals, the frame synchronization allowing the transmitter and receiver to be synchronized in a simple manner. In a preferred embodiment of the invention, a voltage converter connected to the light receiver is arranged in the sensor head, which serves to supply voltage in the sensor head, and the microprocessor monitors the voltage that can be tapped from the energy converter of the voltage converter.

In the measuring system according to the invention, the energy is supplied optically, which enables potential isolation in a simple manner. By monitoring the voltage, only as much energy as necessary is transmitted, which results in a longer lifespan for the light transmitter / laser diode. Light pulses are preferably generated using the pulse width modulation method (instead of amplitude modulation), so that the energy consumption can be optimized. Furthermore, a defined start-up / shutdown behavior (especially communication) only takes place when the necessary voltage has been reached. -

Preferably, according to claim 10, an amplifier is arranged in front of each light transmitter and further a further amplifier is arranged downstream of the light receiver in the central measuring device. "

The use of amplifiers allows the energy-saving mode of operation and the flawless functioning of the light transmitters / laser diodes at the same time by generating only the necessary current for them.

Finally, according to claim 11, the central measuring device has at least one interface circuit and in the central measuring device there is a digital signal processor connected to the microprocessor, which can be configured and read from the outside via the interface circuit. As a result, the digital signal processor can be read out from the outside as well as configurable / programmable in a simple manner, so that, for example, other calculations can be set.

Further advantages and details can be found in the following description of a preferred embodiment of the invention with reference to the drawing. The drawing shows:

FIG. 1 the block diagram of the entire measuring system,

FIG. 2 shows the block diagram of an embodiment of the sensor head according to the invention,

FIG. 3a the structure of a transmission telegram, FIG. 3b, 3c the data transmission at two different sampling frequencies and FIG. 3d the time course of the energy transfer to the sensor head,

FIG. 4 shows an example of the temperature response of the reference voltage VR _e f,

FIG. 5 an example of the characteristic field with compensation parabolas,

FIG. 6a and 6b the timing diagram for the control by the microprocessor in the sensor head,

FIG. 7 shows the block diagram of a second embodiment of the sensor head according to the invention,

8 shows the processing sequence for the interpolation of the measured values (n-2) and (n-1) according to (n) and FIG. 9 the processing sequence for the correction factor determination.

The in FIG. 1 block diagram of the entire measuring system is preferably used for voltage and / or current measurement in medium or high voltage systems; this can also be used in mining.

For optical signal and energy transmission between a sensor head SK with at least one sensor element S1 and a central measuring device MG, a light transmitter LSI controlled by a microprocessor MP1 (for example a transmission laser with a wavelength between 800 nm and 950 nm) is provided in the central measuring device MG, which is used for Data communication and for the energy supply of the sensor head SK preferably _; emits a light superimposed on an AC and a DC component to a first optical waveguide LW1. , ^• .

The block diagram of a first embodiment of the sensor head according to the invention is shown in FIG. 2, wherein a light receiver LE2 connected to the first optical waveguide LW1 and a microprocessor MP2 are provided in the sensor head SK. According to the invention, the microprocessor MP2, after activation by the light receiver LE2, is used to control the sensor element S1, to record and process the values measured by the sensor element S1 and to transmit the processed measured values to the central measuring device MG. For this purpose, the microprocessor MP2 controls a light transmitter LS2 arranged in the sensor head SK, the data communication taking place via a second optical waveguide LW2 to a light receiver LEI arranged in the central measuring device MG.

The two microprocessors MP1, MP2 carry the transmission, measurement and

Monitoring tasks as. distributed control with bidirectional

Data communication through. Furthermore, according to the invention, the measurement values are preprocessed in the sensor head SK, in particular a measurement value correction and / or Measuring range switchover and / or reprogramming of the filter characteristics and / or automatic adjustment; as will be explained in more detail below.

According to the invention, a frame synchronization signal is transmitted between the central measuring device MG and the sensor head SK, which is used both for energy supply and for deriving a clock signal for block-oriented data transmission (see FIG. 3d). The sensor head SK receives the supply voltage from the light transmitter LSI via the first optical fiber LW1 by means of time-discrete laser pulses, which together with the laser pulse width are a measure of the supply voltage: FIG. 3d shows the laser pulse and LI ^', the pause P, the greatest width of the laser pulse LI is represented by a dotted line. After the laser pulse LI, the central measuring device MG optionally sends a byte long data (plus start and stop bit ST, SB see FIG. 3a). The following parameters can be sent, for example: Measuring range to be set, filter setting, distance between the reference measurements. The data transmission takes place with the method agreed in the parameter exchange, whereby the data security can preferably take place via parity bit and checksum. Each time a frame synchronization signal is detected, a timer starts in the MP2 microprocessor. If the timer runs longer than a pregivable time period, it can be assumed that the supply of the module is faulty. The central measuring device MG is informed of this by a telegram, the sensor head SK goes into an idle state and waits for the next signals from the light transmitter LSI (laser diode). The clock of the laser pulses LI thus controls the time of transmission of the measurement data from the sensor head SK to the central measuring device MG. Each request to send data to the central measuring device MG is identified by the start of a laser pulse LI. The microcontroller MP1 receives two pieces of information about its operating voltage generation for a 2-point control. For this purpose, two voltage comparators report when the laser pulse LI emits too much voltage (upper threshold) or receives too little (lower threshold), so that the laser pulse LI is gradually (decremented, i.e. reducing energy supply gradually or continuously or incremented, i.e., in certain time intervals) Energy supply gradually or continuously increase) is changed (dynamic operation). One bit in the transmission telegram is sufficient for this voltage information, which the sensor head SK reports to the central measuring device MG (increase or decrease). A simple threshold value control to a predefinable threshold value, for example to the lower threshold value, can preferably also be carried out. In this dynamic operation, since the SK sensor head is exposed to large temperature fluctuations, the influences of the measured temperature, reference voltages and offset voltage (measurement against ground) are also taken into account (see explanations below).

An analog-to-digital converter ADC is provided in the sensor head SK and is connected to the microprocessor MP2. In normal operation, the microprocessor MP2 reads in the digitized measured value MW (see FIG. 3a) from the analog-digital converter ADC, carries out error correction and coding, and sends the corrected and coded data serially to the central measuring device MG via the second optical fiber LW2 , The sensor head SK has a multiplexer MUX, the inputs of which are each connected to sensor elements S1 (FIG. 2, FIG. 7), the. Measuring channel switchover KU takes place by means of the microprocessor MP2. An impedance converter IW for the tapped measurement value is connected to the output of the multiplexer MUX, and a differential amplifier DV with adjustable gain is arranged between the output of the impedance converter IW and the input of the analog-digital converter ADC, which serves for measuring range switchover BU and is controlled or controlled by the microprocessor MP2 is switched with adjustable gains. Furthermore, the sensor head SK has a reference voltage source REF. The microprocessor MP2 generates a correction (for example three-point calibration) from the measurement of the reference voltage. With this calibration measurement system according to the invention eliminates the Gain - Error and offset - error (. As long as the non-linearity is negligibly small), the ^"relevant temperature-dependent reference voltage value is supplied via an input of multiplexer MUX or a control input of the analog-to-digital converter ADC , Furthermore, a filter FI connected to the light receiver LE2 is arranged in the sensor head SK, at whose output the frame synchronization signal and / or the subsequent data signal can be tapped and fed to the microprocessor MP2. In this way, the rising edge of the frame synchronization signal at the beginning of each data transmission, ie the laser pulse, can be recognized (comparator). Furthermore, a voltage converter SPW connected to the light receiver LE2 is arranged in the sensor head SK and serves to supply voltage in the sensor head SK (including the amplifier V2), the microprocessor MP2 monitoring the voltage which can be tapped from the energy store of the voltage converter SPW.

With the in FIG.2 or -FIG. 7 embodiments shown - the sensor element S1 for DC or AC voltage measurement has an ohmic voltage divider and / or for current measurement an inductive current transformer with downstream filter F1 for transient and high-voltage pulse filtering and a protective element SCH (for overvoltage) arranged in series therewith. When measuring with a measuring shunt, the voltage at the measuring shunt is measured at four points to reduce the thermal voltage, with the measuring lines being twisted and shielded and connected to a terminal block. The terminal strip and also the four inner and outer screens are bridged on the terminal strip. The potential of the shields serves as the reference potential in the sensor head SK and it is possible to connect several sensor heads SK (see FIG. 7) in parallel for measuring a measuring shunt.

Furthermore, a temperature sensor TS is arranged in the sensor head SK and is connected to one of the inputs of the multiplexer MUX. The microprocessor MP2 calculates a correction value from the temperature and, for example, the temperature increase caused by the current flow through the shunt. With the help of this correction value and a shunt correction value (see system information S1), the error caused by the temperature change is compensated. In order to achieve a DC-free and secure transmission, the data are coded according to the invention before transmission. FIG. 3 a shows the structure for an embodiment of a send telegram. The 16-bit wide data word MW supplied via the analog-to-digital converter ADC is segmented by the microprocessor MP2, for example into four bits, and these words are converted into a 7-bit code table stored in the microprocessor MP2 or a memory (not shown) encoded wide words (with segmentation information). In addition to these four words, a word with system information S1 is preferably sent (voltage control, temperature, etc.).

In this embodiment, the expected data volume is calculated from the blocks sent per frame. For the in FIG. 3a example shown; 45 bits must be transmitted for a converted value of 16-bit width after coding (including start and stop bits ST, SB), which corresponds to a block. Depending on the desired sampling frequency, different numbers of blocks have to be sent in one frame. Since the number of blocks must be an integer n, no sampling frequencies can be set. Below are some examples of transmission rates at different sampling frequencies:

tframe: l lδμs

Lfsample = 17.86 kHz; Transfer rate = 45 bit * 17.86 kHz = 803.7 kbit / s

tframe: 156μs Lfsample = 12.82 kHz; Transfer rate = 45 bit * 12.82 kHz = 576.9 kbit / s

tfirame: 118μs

Lfsample = 59.3 kHz; Transfer rate = 45 bit * 59.3 kHz = 2.67 Mbit / s

tframe: 156μs Lfsample = 57.7 kHz; Transfer rate = 45 bit * 57.7 kHz = 2.6 Mbit / s'

The frame structure at two different sampling frequencies, namely preferably a sampling frequency of 60 kHz, is shown in FIG. 3b and sampling frequency 10 kHz is shown in FIG. 3c.

In order to increase the measurement accuracy, the digitized ones are used according to the invention. Measured values MW (for example voltage values) an error correction can be carried out. The correction factors required for this are determined by a periodic adjustment process by the microprocessor MP2 arranged in the sensor head SK and are used for correction until the next adjustment. Since no current measuring voltage value MW can be read in and processed during the reading in of an adjustment value, according to the invention, instead of the regular value

, interpolated value coded and transmitted. The processing sequence for the interpolation of the measured values (n-2) and (n-1) according to (n) is shown in FIG. 8 and the processing sequence for the correction factor determination is shown in FIG. 9 shown; The difference to normal operation is emphasized by the word "or". The interpolation of the measured values (n-2) and (n) after (n-1) results in an analogous manner (not shown). By storing the two measured values (n-2) and (n), between which the adjustment process (n-1) lies, an interpolation of the measured value (n-1) can be carried out. " The interval between the acquisition of the adjustment values is preferably in the range of minutes.

Furthermore, in the measuring method according to the invention, the reference voltage in the climatic cabinet is measured from the outside using a precise measuring instrument. The measured values measured, for example, at temperatures of -40 ° C, 0 ° C and + 85 ° C are stored in the MP2 microprocessor; an example of this is shown in FIG. 4 shown. The measured values describe a parabola that is used for error correction. With the parabola equation it is possible to have one for every temperature Determine the value for the reference voltage. According to the invention, a table with intermediate values is created as follows using a parabola equation:

Δθ = + 85 ° C - (-40 ° C) = 125 ° C

L 1 voltage value / ° C = 125 voltage values (16-bit width) L Memory requirement: 16 bits * 125 = 2000 bits = 250 bytes

In the adjustment process, for example, two voltages and GND successively digitized by the ADC analog-to-digital converter. In addition, the current temperature of the assembly / sensor head SK is determined by means of the temperature sensor TS. With these parameters, an error correction can be carried out as follows.

With the current temperature, the value of the reference voltage can be determined from the table. The compensation parabola is calculated with the real value of the reference voltage (temperature-dependent), the measured values of the reference voltage (pos., Neg.) And the offset at GND.

I y. = aX _j ² + bx _j + c with y, = real value V _Ref (pos.); x, measured value V _Ref

II y ₂ = ax ₂ ² + bx ₂ + c with y ₂ = real value V _Ref (neg.); x ₂ = measured value V _Ref III y ₃ = ax ₃ ² + bx ₃ + c with y ₃ = real value GND (= 0V); x ₃ = measured value GND

-

Accordingly, a system of equations with three unknowns has to be solved, the compensation parabola determined, the correction factors (a, b, c) stored and used until the next adjustment.

Correction calculation: v _input = av _measurement ² + bv _measurement + c

This means that two multiplications and two additions must be carried out to correct a measured value. When using a best-fit line instead of a parabola, the correction method is reduced to multiplication and addition. In addition, the correction factors can be determined with less computational effort, the temperature correction calculation of the measurement value obtained, for example, from the measuring shunt, using a polygon stored in the microprocessor MP2 and the temperature of the shunt (via the measured temperature in the sensor head SK) being carried out (the aging of the measuring shunt is carried out at not taken into account in the error calculation). The time interval between the reference measurements is communicated by the microprocessor MP1 to the microprocessor MP2 of the sensor head SK during the parameterization, no measurement value being recorded during a reference measurement and the previous measurement value being transmitted. In order to ensure a low jitter (a few hundred ns) between the individual measurements, the measured value is recorded directly with the frame synchronization signal.

In FIG. 6a shows an interface circuit (serial peripheral interface) arranged between the analog-digital converter ADC and the microprocessor MP2. The SPI interface is based on an 8-bit shift register. The clock (SCK) is provided by the microprocessor MP2. Clock generation by the microprocessor MP2 only takes place when data is being sent. SCK is idle between transmissions. Sending and receiving take place simultaneously. While the microprocessor MP2 is sending its data, the data is received by the analog-to-digital converter ADC. It follows that data must always be sent, even when nothing is being received. The in FIG. The data exchange shown in FIG. 6a shows the following: Data to SDO are sent with the falling edge, data to SDI are received with the rising edge. The SCK resting level is HIGH.

The interaction between the ADC analog-digital converter and the MP2 microprocessor is described below. Data from the MP2 microprocessor must be kept be sent so that a clock is generated for the analog-to-digital converter ADC. This data is dummy data with no information content, with sending and receiving taking place simultaneously. In total, 24 bits = 3 bytes must be sent for one conversion cycle. After the first byte has been transferred, which is signaled by an interrupt, the receive buffer must be read in the interrupt service routine and a new byte must be written to the transmit buffer. During this time, the interface circuit SPI does not deliver a clock to the analog-digital converter ADC, which means that the latter does not work either. No data is lost. After handling of the interrupt service routine, a byte is sent to the analog-digital converter ADC and one is received at the same time. The timing diagram for control by the microprocessor MP2 is shown in FIG. 6a and 6b. , ,

The entire conversion cycle requires 24 cycles, with the time for handling the interrupt service routine having to be added twice. Tasks in the interrupt service routine are:

- Read the receive buffer

- Write the transmit buffer

L The interrupt is cleared when writing to the transmit buffer or reading from the receive buffer.

The ADC analog-to-digital converter can possibly be activated by connecting the MOSI pin (master out, slave in) to the ADC analog-to-digital converter. The analog-digital converter ADC can be activated or deactivated by sending appropriate data. The MUX multiplexer enables reference voltages to be applied to the ADC analog-to-digital converter. These tensions. are used by the MP2 microprocessor to correct the gain errors that occur on the analog path. The correction calculation can be switched off in order to obtain the pure measurement data of the ADC analog-digital converter in test mode. ^{■ '■} The power loss of the measuring system according to the invention was determined in extensive test series as follows:

The power loss of the voltage reference REF and the multiplexer MUX can

_{* be} neglected.

A second embodiment with multiple sensor heads is shown in FIG. 7, using identical reference numerals.

The measuring system according to the invention is used wherever high demands are placed on the optical signal and energy transmission and a maximum of efficient and secure measurement data transmission must be ensured, for example in mining, in medium or high voltage systems or in industrial electronics, in particular automation technology , According to the invention, dynamic operation based on the frame synchronization signal and a Pulse width modulation is carried out in conjunction with a two-point control or simple threshold value control (fine adjustment), the measurement values MW, which are inherently faulty, are corrected with the aid of the ambient temperature measured in the SK sensor head, the measured reference voltages and the measured offset voltage in the SK sensor head and, depending on the operating state, between the two Microprocessors MP1, MP2 as distributed control with bidirectional data communication transfer parameters or data and the data / messages according to their data transmission quality and on time

Arrival monitored.

In a further embodiment of the invention, for example, the measuring system according to the invention can be used in the context of real-time networking of controls (also real-time control via Ethernet or Powerlink), where the synchronizability of the participants (for example drives, fast I / Os, sensors, actuators, vision systems) with one another and the processing of the data in the control cycle of the drives is a prerequisite; the temperature TS is connected to the microprocessor MP2 via the interface circuit SPI and is queried cyclically by the latter; Instead of the microprocessors, programmable logic for the preprocessing of the measured values can also be used; Sensor signals supplied to the microprocessor MP1 from external sensors S1 via a digital signal processor DSP can be fed in, among other things.

Claims

claims

1. Measuring system for medium or high voltage systems or in mining with optical signal and energy transmission between a central measuring device

(MG) and a sensor head (SK) with at least one sensor element (Sl), in which

5 »in the central measuring device (MG) controlled by a microprocessor (MPl)

Light transmitter (LSI) is provided, which for data communication and

Power supply of the sensor head (SK) emits a light superimposed on various components to a first optical fiber (LW1),

• in the sensor head (SK) one connected to the first optical fiber (LW1)

10 light receiver (LE2) and a microprocessor (MP2) are provided, the microprocessor (MP2) after activation by the light receiver (LE2) to control the sensor element (Sl), the detection and processing of the

Sensor element (Sl) serves measured values and data communication for

Transmission of the processed measured values to the central measuring device (MG) via

15 controls a light transmitter (LS2), a second optical waveguide (LW2) and a light receiver (LEI) arranged in the central measuring device (MG) such that the two microprocessors (MPl, MP2) transmit, measure and

Monitoring tasks as distributed control with bidirectional

Perform data communication using a frame synchronization signal

'20 serves both for energy supply and for the derivation of a clock signal for block-oriented data transmission and a data communication for parameterization and / or programming between the central measuring device

(MG) and sensor head (SK) as well as preprocessing of the measured values in the

Sensor head (SK), in particular a measured value correction and / or a

25 Measuring range switchover and / or reprogramming of the

Filter characteristics and / or an automatic adjustment in the sensor head (SK) is carried out.

2. Measuring system according to claim 1, characterized in that in the sensor sensor (SK) an analog-digital converter (ADC) is provided, which is connected to the microprocessor (MP2), and that the ^" microprocessor (MP2) the over the analog to digital converter (ADC) supplied digital measurement value (MW) is corrected and / or supplemented with information with system information (SI), segments the resulting ^'data coded by block coding and provides it with information on the segmentation, so that a DC-free and error-correcting data transmission is made possible.

3. Measuring system according to claim 1, characterized in that the sensor head (SK) has a multiplexer (MUX), the inputs of which are each connected to sensor elements (S1), the measuring channel switching (KU) being carried out by means of the microprocessor (MP2).

4. Measuring system according spoke 2 and 3, characterized in that on

Output of the multiplexer (MUX) an impedance converter (IW) for the

'tapped measured value is connected and that between the output of the

Impedance converter (IW) and input of the analog-digital converter (ADC)

Differential amplifier (DV) is arranged with adjustable gains, which is connected to the microprocessor (MP2) for measuring range switching (BU). ^•

5. Measuring system according to claim 1, characterized in. that the sensor element (Sl) has a 'ohmic voltage divider for DC or AC voltage measurement and / or an' inductive current transformer with downstream filter (F1) for filtering transients and high-voltage pulses and serially arranged protective element (SCH) for measuring the current.

6. Measuring system according spoke 1 and 3, characterized in that a temperature sensor (TS) is arranged in the sensor head (SK), which is connected to one of the inputs of the multiplexer (MUX).

7. Measuring system according to spoke 2 and 6, characterized in that the sensor head (SK) has a reference voltage source (REF) and that for adjustment controlled by the microprocessor (MP2) the respective temperature-dependent reference voltage value (VR _e f) via an input of the multiplexer ( MUX) or, a control input of the analog-digital converter (ADC) can be fed.

8. Measuring system according to claim 1, characterized in that a filter (F1) connected to the light receiver (LE2) is arranged in the sensor head (SK), at its output the frame synchronization signal and / or the subsequent data signal can be tapped and the microprocessor (MP2) is feedable. ^'

9. Measuring system according to one of claims 1 to 8, characterized in that in the sensor head (SK) with the light receiver (LE2) connected voltage converter (SPW) is arranged, which for

Power supply in the sensor head (SK) serves and that the microprocessor

(MP2) monitors the voltage that can be tapped at the energy storage device - the voltage converter (SPW).

10. Measuring system according spoke 1, characterized in that an amplifier (VI, V2) is arranged in front of each light transmitter (LSI, LS2) and that a further amplifier (V3) is arranged downstream of the light receiver (LEI) in the central measuring device (MG).

11. Measuring system according to claim 1, characterized in that the central measuring device (MG) has at least one interface circuit (10) and that in the central measuring device (MG) with the microprocessor (MPl) connected digital signal processor (DSP) is arranged, which via the interface circuit (S 1) can be configured from the outside and can also be read out.

12. Method for measuring currents or voltages in medium or high voltage systems and in mining with optical signal and energy transmission between a central measuring device (MG) and a sensor head (SK) with at least one sensor element (Sl) according to one of the

Claims 1 to 11, characterized in that microprocessors (MPl, MP2) arranged in the measuring device (MG) and in the sensor head (SK) carry out transmission, measurement and monitoring tasks as distributed control with bidirectional data communication, that the arranged in the measuring device (MG) Microprocessor (MPl) after the energy transfer in dynamic operation

The requirement of a frame synchronization signal controls that, for preprocessing the measured values and / or for automatic adjustment in the sensor head (SK), the reference voltage is measured in the climate chamber and stored in at least one microprocessor (MPl, MP2) and that the microprocessor arranged in the sensor head (SK) MP2) carries out an adjustment process and an error calculation and controls a DC-free and error-correcting data transmission.

13. The method according to claim 12, characterized in that the fine adjustment of the energy transmission is carried out by means of a pulse width modulation in conjunction with a two-point control or a simple threshold control and that before the data transmission the measurement values (MW), which are inherently faulty, with the aid of the ambient temperature measured in the sensor head (SK) , Reference voltages and offset voltage in the sensor head (SK) can be corrected.