Single Phase Voltage Relays for Agricultural Pumps: RN-119 & RN-102

When the Grid Fails Your Pump — and Nobody Warns You in Time

Every monsoon season, the same distressing calls arrive from farmers and agri-business operators across India. 'My submersible pump burned out again — third time this year.' The motor rewind shop is two towns away, the bore well is dry while the crop is wilting, and the replacement cost runs into tens of thousands of rupees. What nobody told the farmer is that his 2 HP submersible motor did not burn out because it was defective. It burned out because the rural feeder voltage swung from 265 V down to 155 V in the space of forty minutes during peak irrigation hours — and nothing disconnected the pump before the motor windings cooked themselves.

This is not an isolated story. It is the defining electrical protection gap in Indian agricultural infrastructure today, and it is exactly the problem that the Novatek Electro RN-119 and RN-102 single phase voltage monitoring relays are engineered to close.

Why Agricultural Feeders Suffer Such Extreme Voltage Swings

Understanding the protection problem requires a brief look at the electrical engineering reality of rural distribution networks in India.

High-Impedance Distribution Lines

Rural 11 kV feeders often run 15–40 km from the substation to the last distribution transformer. At that distance, the line impedance is significant. When fifty pumps start simultaneously at 6 AM — which is common in canal-irrigated belts — the inrush current of each motor creates a cumulative voltage drop that the feeder cannot recover from quickly. Terminal voltage at the pump control panel can fall well below 180 V.

Solar and Renewable Energy Integration Instability

As solar pump controllers and rooftop PV systems are added to these feeders, voltage regulation becomes even more unpredictable. During cloud-cover transients, solar inverter output collapses in milliseconds. If the grid is simultaneously weak, the pump motor — still spinning — sees a voltage dip that the standard thermal overload relay is far too slow to respond to. The motor draws excess current, heat builds up in the windings, and insulation breakdown follows.

Neutral Displacement and Open-Neutral Faults

In single-phase rural connections, a corroded or mechanically failed neutral conductor at the pole-mounted distribution box is alarmingly common. When neutral is lost, the phase-to-neutral voltage at the appliance becomes indeterminate — it can swing to near phase-to-phase voltage (415 V) depending on other connected loads, destroying pump motor windings and capacitors instantly.

Overvoltage During Light-Load Periods

During early morning or late night hours when agricultural loads are switched off, the same feeder that was undervoltage at noon can be overvoltage. Capacitor banks meant to correct power factor during heavy load now push voltage above 250 V when load is light. Motors left running for drip timers, cold-chain compressors, or grain dryer fans suffer insulation stress from sustained overvoltage.

The Solution: RN-119 and RN-102 Single Phase Voltage Monitoring Relays

Novatek Electro's RN-119 and RN-102 are purpose-built single phase voltage monitoring relays that continuously measure supply voltage and disconnect the protected load the moment voltage moves outside safe operating limits. They protect against undervoltage, overvoltage, and open-neutral (neutral break) conditions — all three of the dominant fault modes in agricultural single-phase supplies.

RN-119 — DIN Rail Mount, 10–16 A, Compact Protection for Panel Integration

The RN-119 is a 2-pole, DIN-rail-mounted single phase voltage monitoring relay rated for 220–240 V AC supplies with a contact rating of 10–16 A SPDT (1NO + 1NC). Its compact form factor makes it ideal for integration inside submersible pump control panels, irrigation timer enclosures, and solar pump controller cabinets. The SPDT output allows both normally-open load-switching and normally-closed alarm or signalling circuits to be driven simultaneously from a single relay — a wiring advantage in compact rural panel builds.

Price: Rs. 1,950 per piece (ex-GST). GST @ 18% applicable extra.

RN-102 — Wall-Mount, 32 A, Heavy-Duty Protection for High-Power Pumps

The RN-102 is a wall-mounting type single phase voltage monitoring relay rated for 220–240 V AC with a significantly higher contact capacity of 32 A SPDT. This makes it the preferred choice for controlling contactors driving 3–5 HP submersible pumps, grain-processing motors, and cold-chain refrigeration compressors — loads where the pump contactor coil or the load itself draws currents that the lighter RN-119 contact is not rated for. The wall-mount enclosure suits surface-mounted rural installations where a DIN rail panel is not available.

Price: Rs. 4,570 per piece (ex-GST). GST @ 18% applicable extra.

Technical Specifications at a Glance

Quick Selection Guide — Which Model for Which Application?

Application Categories Where RN-119 and RN-102 Are Deployed

1. Submersible Pump Sets for Bore Well Irrigation

Single-phase submersible pumps from 0.5 HP to 5 HP are the most voltage-sensitive loads in agricultural infrastructure. The long cable run from panel to pump adds resistance, making terminal voltage at the motor even lower than at the panel during undervoltage events. The RN-119 and RN-102 protect the motor by disconnecting power before sustained undervoltage causes thermal damage to stator windings.

2. Drip and Sprinkler Irrigation Control Systems

Modern drip irrigation systems include solenoid valves, filter backwash motors, fertilizer dosing pumps, and PLCs — all powered from a single-phase supply. An overvoltage or neutral-break event does not just damage one motor; it can destroy the entire controller electronics. Installing an RN-119 upstream of the irrigation controller panel provides a first line of defence for the entire system.

3. Grain Processing and Post-Harvest Equipment

Rice hullers, grain dryers, dehuskers, and seed-grading machines in rural mandis and farm cooperatives are frequently powered by single-phase supplies on weak agricultural feeders. These loads operate continuously for 8–12 hours during harvesting season — precisely when grid voltage is most stressed. The RN-102, with its 32 A wall-mount format, suits standalone motor control boxes for this equipment category.

4. Rural Cold-Chain and Agri-Cold Storage

Small-capacity cold rooms (0.5–2 TR) used for vegetable, fruit, and dairy storage in rural areas are increasingly powered by single-phase connections. A compressor that starts under low voltage draws excessive locked-rotor current, overheats, and fails prematurely. The RN-102 prevents compressor start-up under unsafe voltage and disconnects immediately if voltage dips during operation.

5. Solar-Grid Hybrid Pump Systems

As PM-KUSUM and state solar pump schemes expand, hybrid solar-grid pump controllers are proliferating. These systems switch between solar inverter output and grid supply. During grid-solar transition moments, voltage transients occur. An RN-119 on the grid input side of the control panel provides an independent hardware protection layer that operates regardless of the inverter's internal software state.

Why Novatek Electro?

• ISO 9001:2015 Certified Manufacturing: Every RN-series relay is manufactured under a documented quality management system, ensuring consistent performance across production batches.
• CE Certified Products: CE marking confirms that RN-119 and RN-102 meet European safety and EMC directives — a benchmark of quality relevant to export-oriented agri-processors and equipment OEMs.
• Made in India, Designed for Indian Grid Conditions: Novatek Electro products are engineered specifically for the voltage variation patterns, power quality challenges, and ambient conditions found on Indian distribution networks.
• 30+ Years of Electrical Protection Expertise: With over three decades of manufacturing protection relays from our Delhi facility, Novatek Electro brings deep domain knowledge to product design and after-sales technical support.
• Nationwide Distributor and OEM Network: RN-series relays are available through authorised distributors and online via Intelli-Electro, with technical support accessible directly from the manufacturer.

Frequently Asked Questions