MELPRO-S, compact digital overcurrent and voltage protection relays
MELPRO-S is a series of compact microprocessor protection relays for high and extra-high voltage distribution networks. It includes overcurrent relays with three-phase protection and earth fault protection, and three-phase undervoltage and overvoltage relays. The relays are installed in incomer, outgoing feeder and busbar sectionalising cells.
- Models
- overcurrent relays (3 phases + earth fault), voltage relays (3-phase min./max.)
- Time-current characteristics
- 16 kinds
- Self-diagnostics
- continuous monitoring from input to output
- Features
- low burden (smaller CTs and VTs), compact case for replacing old relays
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
MELPRO-S relays combine protection, control and monitoring of the network in a small case. The series is used at substations, industrial plants and infrastructure facilities. Current relays protect three phases and respond to earth faults. Voltage relays monitor three phases against undervoltage and overvoltage settings and are used for busbar protection of switchgear. In an incomer cell the current relay provides backup for feeder protection, and in a line cell it trips first on a fault.
The delayed element offers 16 kinds of time-current characteristics. The characteristic is chosen so that it coordinates with the overcurrent protection at the supplying distribution substation. This makes it easier to set selectivity between the protection of the substation feeding the network and the protection of the consumer's cells. The more closely the curve follows the characteristic of the upstream protection, the smaller the selectivity interval that can be allowed and the faster a short circuit near the source is cleared.
Self-diagnostics continuously check the electronic circuits from input to output. An internal fault is detected before it causes incorrect protection operation or damage in the power system. For the relay protection and automation service this means that a hidden relay failure will not wait for the next scheduled check.
The burden of the relay is low. Therefore current and voltage transformers of smaller size can be chosen, and the energy losses of the measuring circuits are reduced. The compact case is designed to save space in the relay compartment. It is convenient to fit in place of existing relays when switchgear is modernised and old relays are replaced with digital ones.
The relays work together with peripheral equipment of the manufacturer. For earth fault protection, zero-sequence current transformers (ZCT) and zero-sequence voltage detectors (ZVT) are used. The sensitivity of earth fault protection depends on the correct choice of ZCT. The ZCT encloses all three phases of the cable and measures the zero-sequence current directly, without a filter of three phase current transformers. For neutral earthing through a resistor, the manufacturer supplies current-limiting resistors. The set of relays and peripherals is selected for the cell arrangement, that is incomer, outgoing feeder or sectionalising breaker.
Technical specifications
| Models | overcurrent relays (3 phases + earth fault), voltage relays (3-phase min./max.) |
|---|---|
| Time-current characteristics | 16 kinds |
| Self-diagnostics | continuous monitoring from input to output |
| Features | low burden (smaller CTs and VTs), compact case for replacing old relays |
Request a price and lead time
MELPRO-S, compact digital overcurrent and voltage protection relays. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 8536 49 00 00 |
|---|---|
| HS, 6 digits | 8536 49 |
| CN (EU) | 8536 49 00 |
| HTSUS (USA) | 8536 49 00 85 |
| China customs tariff | 8536 49 00 00 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
Which protection functions do MELPRO-S relays have?
Current relays provide three-phase overcurrent protection and earth fault protection. Voltage relays monitor three phases against minimum and maximum voltage.
How many time-current characteristics are available?
The delayed element offers 16 kinds of characteristics. The curve is chosen to coordinate with the protection of the supplying substation.
Are MELPRO-S suitable for replacing old relays?
Yes, the compact case is designed to replace existing relays during modernisation. Low burden allows smaller current and voltage transformers.
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