The measuring devices of the SHERLOG range combine the monitoring functions of a high-class digital fault recorder with the features of a power quality analyser in a single system. They can be used to comprehensively monitor power engineering equipment such as lines and busbars and associated protection devices and switchgear equipment.

As well as detecting faults and making high-resolution recordings of the signal characteristics in fault records, SHERLOG systems can also make long-term recordings of RMS value characteristics and calculate all the relevant power system parameters needed in order to determine and monitor power quality.
Because SHERLOG devices can be easily networked, it is possible to create highly complex measuring systems which are capable of monitoring any number of bus bars and lines.

SHERLOG can be used to monitor power systems precisely and reliably. As SHERLOG systems are entirely digital, their functioning is fully software-controlled. All processes and functions are freely programmable. New function modules or algorithms which meet new standards can easily be added during manual or automatic software maintenance. The NRGCenter software package is used to configure and control SHERLOG measuring instruments and to read out, archive and evaluate the recorded data.

Fields of application

SHERLOG systems are used in all the parts of an electricity supply network, from power generation and transmission right on through to the end user. They are suitable for all voltage levels.

Examples of applications:   

1. Fault recorders for power stations, transformer substations and transmission networks at low, medium, high and extra-high voltage levels. Two simultaneous sampling frequencies of between 100 Hz and 30 kHz can  record even extremely short events with precision and allow comprehensive analysis as well as fault location.
2. Capture of slow events such as power swings and transient phenomena.
3. Continuous recording of all power system parameters with up to 8 simultaneous density levels for applications such as:
   1. Power quality recording to EN50160, for example
   2. Load and frequency recording
   3. Analysis of power consumption
   4. Capture of influences resulting from a constantly fluctuating generator and load structure
   5. Monitoring of general or individually agreed connection conditions for compliance with limit values
4. Documentation system for commissioning and service tests
5. Chronological event recording and logging of binary status signals. Individually definable event classes, message texts and acknowledgement requirements make SHERLOG a fully fledged sequence-of-event recorder.

Safe and efficient

1. 

   Because SHERLOG fault recorders contain no parts which are subject to wear and tear, such as hard disk memory or fans, they are 100% maintenance-free.
2. Galvanic separation of all measurement inputs and communication interfaces for maximum flexibility and safe operation.
3. Measurement data is saved reliably in the internal data memory and is not lost in the event of a power failure or when the device is switched off.

Advantages of SHERLOG fault recorders over digital protection relays

1. Trigger criteria can be set independently of protection relays and are much more comprehensive, so that even very slight anomalies in the supply system can be recorded
2. High sample rate for detecting transient faults, malfunctioning transducers, defective switching contacts or resonance phenomena
3. Recordings include information on all the component parts of an installation and their impact chain
4. By recording data continuously in order to monitor power system operation comprehensively, proof of how a power system is operating can be provided at any time, even if no disturbances are detected during the period in question.

Measurement quantities and trigger criteria for analog signals

• Voltage
• Current
• Frequency
• Line angle
• Form and peak factor
• THD, PWHD, THDG, TDD
• Harmonics to the 50th order
• Interharmonics
• Subharmonics (1 Hz to 60 Hz)
• Active power, apparent power and reactive power
• Active energy, apparent energy and reactive energy
• Power factor
• K-factor
• Positive sequence system, negative sequence system and zero sequence system for voltage, current and impedance
• Positive sequence system, negative sequence system and zero sequence system for all subharmonic frequencies from 1 Hz to 60 Hz on all current channels
• Unbalance for voltage, current and impedance
• Impedance
• Flicker (Pst, Plt) to IEC 61000-4-15

Time synchronisation

• GPS synchronisation with internal receiver
• GPS synchronisation with an external central clock
• DCF77
• Synchronisation to PC time
• Seconds and minutes pulse
• KoCoS synchronisation bus

Communication interfaces

• Electric Ethernet
• Ethernet over optical fibre
• USB
• RS485
• Electric RS232
• RS232 over optical fibre
• Internal modem

Power supply

The standard SHERLOG delivery package includes a wide-range power supply unit for flexible powering. Alternatively, SHERLOG can also be equipped with DC power supply units.

• Wide-range power supply unit (85 to 265 VAC / 90 to 350 VDC)
• Optional power supply units (9 to 18 VDC, 18 to 36 VDC, 36 to 72 VDC)

SHERLOG can optionally be equipped with two independent power supply units for redundant mains operation. Because each power supply unit uses its own voltage input, two different power supply units can be chosen (e.g. a wide-range power supply unit and a 24 VDC power supply unit).