Monitoring electrical quantities: System 

Advantages of DOLD’s monitoring solution:

• Undervoltage and overvoltage relays, voltage relays, single- and three-phase:

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Monitoring electrical quantities: Load

Advantages of DOLD’s monitoring solution:

• Current relays

Very wide application range for currents from 2 mA up to 100 A in a compact design. Save space, wiring expense and cost by integrated straight-through current transformer in our CT range.
Metallic isolation from the system: longer service life thanks to insensitiveness to voltage shifts/harmonics.  

• Underpower monitors

Our most compact Cos φ monitor saves the most space and cost.    Monitor asynchronous motors up to 100 A without external current transformer.
Very sensitive measuring for underpower, far better than it would be possible with pure current measuring. 

• Load monitors, overload monitors, load transformers

Very precise replica of the loads occurring during motor operation. This is especially relevant to motors where underpower relays ((Cosφ relays) or current relays would not be sensitive enough to respond in time before an overload condition.

Monitoring electrical quantities: Processes

Advantages of DOLD’s monitoring solution: 

• Speed/stand-still relays

Reliable monitoring for zero speed at machines with rotating parts.

Monitoring of multiple quantities/
specific applications

Advantages of DOLD’s monitoring solution:

• Multifunctional relays

Save space within the switch cabinet. Cost-effective thanks to versatility.

• Measuring relay for specfic applications

Tailored to your specific applications.
Comply with specific norms, e.g. for medical applications

Monitoring electrical quantities: System

Technology:    

• Undervoltage and overvoltage relays, voltage monitors, single- and three-phase:

Arithmetic mean value measurement.
Short-time failure detection with IL 9079: Short-time failures from 20 ms may be due to system transfer or lightning stroke and may cause disturbances during measurements or sensitive processes. Normal voltage relays can not detect this kind of failures. Using the reset function it is possible to cancel processes after a fault. 

•  Phase-sequence relays

Phase-sequence relays check the system for clockwise phase sequence and prevent motors from starting in the wrong sense of rotation.

•  Unbalance relays, phase monitors, phase indicators

Unbalance relays monitor the system for phase failure and are mainly used to protect motive-power loads. Compared to voltage relays they have the advantage that they respond in the case of a system phase failure, even if the missing system phase is generated and recovered by the motor. 

DOLD unbalance relays operate at 6-8% unbalance, i.e. at a voltage variation of approx. 14-18 V.

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• Neutral monitors

Monitor the system for broken neutral conductors and unbalance resulting from this where loads with the largest resistance are exposed to high voltages and may be damaged by them. Use of neutral monitors for ohmic and single-phase motive-power loads.  

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• Frequency relays

Work on the principle of frequency comparison: The measured frequency is compared with a frequency generated in the device and settable on a setting knob.

• Insulation/differential-current monitors

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Monitoring electrical quantities: Load

Technology: 

• Current relays

The arithmetic mean value of the rectified measured current is calculated, with the devices adjusted for sinusoidal AC currents as r.m.s. values. 

• Underpower monitors

Underpower relays monitor the phase angle between current and voltage. As the phase angle changes with the motor load this measuring method is suited for monitoring asynchronous motors for underpower and no load operation independent of their size.  

• Load monitors, overload monitors, load transformers

Load relays monitor the active-power input of electrical loads. The single-phase measuring principle assumes a symmetrical load in all 3 phases as is common with motive-powered loads.

Monitoring physical quantities: Processes

Technology: 

• Speed/stand-still relays

Speed relays work on the basis of the frequency comparison principle. Using a proximity switch the rotational speed is converted in a proportional frequency. This frequency is compared with a frequency which is generated in the device and can be adjusted with a setting knob. If the speed-proportional frequency is higher than the reference frequency generated in the device, the output relay of the underspeed monitor will be energized and that of the overspeed monitor de-energized.  

• Temperature relays, thermistor motor protection relays

The motor protection relay monitors the thermistors integrated in the motor. This will prevent thermal overload due to high switching frequency, single-phase operation, impaired cooling or high ambient temperature, for example. Up to 6 thermistors in series connection can be monitored. A broken sensor line will lead to an immediate cutoff. The products can also be used to monitor wrapped quick-break switches (bimetal thermostats). Temperatures are measured via connected PT100 sensors or PTC resistors.  

• Level sensing relay

The measuring range up to 450 kΩ allows to distinguish between liquid and foam.
High immunity to system interference thanks to low-frequency metallically isolated measuring circuit. Line lengthes to the sensor up to 1500 m possible. No electrolysis effects in liquids by the use of a measuring AC voltage.
Choice of two outputs for min./max. control, also suitable as early warning and limit value disabling device.

Monitoring of multiplequantities/
specific applications

Technology: 

• Multifunctional relays

Critical monitoring functions integrated in a single compact device, e.g. IL 9086, phase relay with thermistor motor protection: detects following faults in three- and four-wire three-phase systems: undervoltage, phase failure, phase sequence, neutral conductor interruption, unbalance, overtemperature, broken conductor in the sensor circuit, short-circuit in the sensor circuit. 1 PTC input for 1 to 6 thermistors. This all either in an installation enclosure or in a switch cabinet with a width of 35 mm.  

• Measuring relay for specfic applications

Special-purpose devices for specific applications are certified according to relevant norms, e.g. DIN VDE 0100-710 for medical areas. 

 Monitoring electrical quantities: System

Applications:

Relays for system monitoring are used to protectequipment and plants, to supply emergency light systems, to detect neutralconductor interruptions and short-time voltage interruptions. The products are equipped with differentfunctions depending on the application and compliance requirements.

• Undervoltage and overvoltage relays, voltage monitors,single- and three-phase:

Protect loads against overload due to poor powersystem quality. Single-phase voltage monitoring, e.g. in control circuits ord.c. control circuits.

• Phase-sequence relays:

Monitor the phase sequence in a three-phase system: Ensure the start ofthree-phase motors in the correct sense of rotation, e.g. pumps or compressors.Signalling via potential-free contact.

• Unbalance relays, phasemonitors, phase indicators

Monitor motors in three-phase systems to prevent reversing andsingle-phase operation and consequences of this. Signalling via potential-freecontact.

• Neutral monitors

Monitor for neutral conductor interruptions to protectconnected devices, e.g. secondary distribution systems in buildinginstallations.

• Frequency relays

System monitoring when power is fed in the system,e.g. small power stations (solar or wind power systems).

Start control for drives with slipringmotors, e.g.mill and crane drives.

• Insulation/differential-currentmonitors

Fire protection in thewood working industry.

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Monitoring electrical quantities: Load

Applications:

• Current relays

Monitor the current flow in single- and three-phase systems, e.g. emergency lighting and motors in pumps, cranes, elevators, ventilators.

• Underpower monitors

Monitor single- and three-phase asynchronous motors undirectionally for underpower and no-load operation, e.g. due to chain and V-belt rupture, shaft rupture, valve blocking or dry-running of fans and pumps.

• Load monitors, overload monitors, load transformers

Used in manufacturing lines, materials handling, packing machines, filling plants or crushing mills, for example. Check for overload due to blocking, sluggishness, tool wearing, clogging, etc.

Monitoring physical quantities: Processes

Applications:

• Speed/zero-speed relays

Monitor machines for a too long or too short work cycle. Avoid risks to man and machinery, e.g. in transport businesses, checking turning lathes for standstill.

• Temperature relays, thermistor motor protection relays

Use in pumps, fans, ball bearings, for example.

• Level sensing relay

Use for filling level monitoring and control of conductive, non-flammable liquids and powder. Protect against overflow and dry-running, e.g. in biological power stations, sewage treatment, irrigating, sprinkling, draining plants, fire extinguishing/lifting pumps.

Monitoring of multiple quantities/

specific applications

Applications:

• Multifunctional relays

A variety of applications, e.g. phase monitor with thermistor protection IL 9086 :  Monitor three-phase systems with motive-power loads and temperature monitoring of loads, e.g. for lifts acc. to EN 81-1, EN 81-2.

• Measuring relay for specfic applications

Special-purpose applications, e.g. in medical rooms, lifts, locomotives, battery systems.