Preventing Dry Running, Overload & Pump Motor Failure in Municipal Systems

Abstract / Standalone Protection Overview: A standalone earth leakage protection relay (such as NewElec’s GA Series) is typically installed when an existing motor protection relay lacks built-in earth leakage or earth fault capabilities. For instance, older installations or systems equipped with basic relays like NewElec’s LA Series or generic competitor products require an external earth leakage device to meet full safety and operational protection standards. Conversely, integrated advanced relays such as the NewCode relay deployed at major facilities like Rand Water Zuikerbosch already include comprehensive on-board earth leakage and earth fault protection, eliminating the need for a separate standalone unit.

How can municipalities reduce dry running, overload and pump motor failure?

Municipal pump protection should be based on the operating risks around the pump, not only the motor size. Dry running, overload, phase problems, earth leakage, cable faults and changing process conditions can all damage pump motors or cause unnecessary downtime. The right motor protection strategy detects these conditions early and isolates the motor before a developing problem becomes a larger failure.

Municipal water systems depend on pumps every day.

Water treatment plants need pumps to move water through treatment and distribution. Wastewater facilities rely on sewage and transfer pumps. Boreholes, booster stations and flood-control systems each have their own operating demands.

When one of these pumps stops unexpectedly, the problem is rarely limited to the motor itself.

A failed pump can affect process flow, reduce system capacity, increase pressure on standby equipment and create additional work for already stretched maintenance teams.

That is why NewElec’s municipal motor protection solutions approach pump protection around the application and operating risk rather than treating every municipal motor as the same.

For South African municipalities in particular, this matters where newer equipment often operates alongside ageing pumps, MCCs, cabling and control systems.

Pump motor failure is not always an electrical problem

A motor may trip because of an electrical fault, but what caused the electrical condition in the first place?

A blocked pump can increase mechanical load. A sump running empty can leave a pump operating without sufficient water. A falling borehole level can change the load on the motor. Damaged insulation can create earth leakage. Supply problems can affect current balance.

In other words, the electrical condition seen by the protection relay is often the result of what is happening in the pump and process.

This is why municipal pump protection should start by asking:

• What type of pump is being protected?
• What happens when the water level changes?
• Can the pump become blocked or clogged?
• Is dry running possible?
• Is the motor submerged?
• Does the application use a VSD?
• How critical is the pump to municipal operations?
• What information does the maintenance team need after a trip?

NewElec’s water treatment pump protection solutions provide a useful starting point because they consider pump applications and their operating risks, rather than simply motor ratings.

Dry running is one of the most important pump risks to detect

Dry running occurs when a pump continues operating without sufficient fluid.

That can happen when a sump empties, a borehole water level drops, an intake becomes restricted or the incoming water supply is interrupted.

For centrifugal pumps, insufficient flow can remove the cooling and lubrication the pump depends on, contributing to overheating and damage. In dewatering applications, submersible pumps can also overheat when the surrounding water level drops because the water itself helps cool the motor.

The important point is that the motor may still be electrically connected and running.

The problem is that it is no longer operating under the load conditions expected during normal pumping.

That makes minimum-load or load-loss protection particularly useful for pump applications.

NewElec’s Relay Selection Assistant specifically includes Load Loss (Dry Run) among the protection functions engineers can use when filtering the three-phase motor protection relay range.

Instead of waiting for heat or mechanical damage to tell the maintenance team that something has gone wrong, the protection strategy can use changing motor load as an indication that the pump may no longer be doing useful work.

Why underload protection matters for municipal pumps

Overload receives a great deal of attention in motor protection.

But with pumps, too little load can sometimes be just as informative as too much load.

When a pump loses its medium, the mechanical load on the motor can fall. If the protection relay can detect that reduction and compare it to an appropriate threshold, it may be possible to trip the motor before the pump remains in a damaging dry-run condition.

NewElec’s MA technical guidance describes this approach directly for sump-pump applications: the relay can monitor a decrease in load, apply an underload threshold, and use a selectable trip delay.

That makes underload or load-loss protection especially relevant for:

• Borehole pumps
• Sump pumps
• Dewatering pumps
• Transfer pumps
• Water storage and reservoir applications
• Pumps where inlet conditions can change significantly

Municipal teams reviewing these applications can explore the MA Series Relay alongside other NewElec motor protection options.

The key is not simply to turn on an underload function. The threshold and delay need to make sense for the normal operating behaviour of that particular pump.

Overload often tells you something has changed in the pump system

At the opposite end of the load spectrum is overload.

A pump motor drawing more current than expected may be experiencing increased mechanical or process resistance.

For municipal systems, possible contributors include:

• A blocked or partially blocked impeller
• Debris entering the pump
• Bearing deterioration
• Mechanical binding
• An operating point outside the intended range
• Increased density or solids in the pumped medium
• Electrical supply problems
• Pump or motor deterioration

Wastewater and dewatering pumps are particularly exposed to solids and debris. Research into South African pumping applications identifies blockages, sludge, sand, debris and foreign objects as common causes of pump problems, with a blocked impeller potentially resulting in a stalled motor or shutdown.

This is why simply resetting an overload trip does not solve the underlying problem.

A repeated overload is information.

The maintenance team needs to establish why the load increased.

NewElec’s KD Series motor protection range is relevant to pump applications where more comprehensive protection and diagnostic information are required. NewElec’s current selection guidance describes the KD Series as providing functions including thermal overload, earth leakage, short circuit, stall, jam, voltage, frequency and power-factor protection, together with event and fault records.

Blocked wastewater pumps create a different protection problem

Wastewater pumps deserve particular attention because the medium itself can create mechanical problems.

Municipal sewage systems may carry fibrous material, solids and unexpected debris. When material becomes lodged in the pump, the impeller may become restricted or stop moving freely.

The result can be an increase in motor load.

If the blockage becomes severe enough, the motor can stall.

A municipal wastewater protection strategy should therefore consider the relationship between:

Pump blockage → increasing mechanical resistance → increased motor load → overload/stall → motor heating or trip

That sequence helps explain why motor protection should be selected around the pump application instead of simply asking how many kilowatts the motor is rated for.

NewElec’s Municipal Motor Protection page includes wastewater and sewage pumps among the core municipal applications where appropriate motor protection can support more reliable operation.

The aim should not be to stop pumps unnecessarily. It should be to distinguish normal operating changes from conditions that are moving towards equipment damage.

Submersible pumps introduce electrical risks as well as mechanical ones

Submersible pumps operate in an environment where the motor and electrical system must remain isolated from the surrounding water.

That makes cable condition, seals and insulation particularly important.

Research into submersible pump failures identifies several electrical risks, including damaged power cables, thermal overload and water entering the motor through failed seals or cable-entry points. Water ingress can lead to ground faults and eventual motor failure.

This is where earth leakage protection becomes part of the broader pump-protection conversation.

NewElec’s GA Series Earth Leakage Relay provides dedicated earth leakage and earth fault protection. The GA Series also incorporates harmonic suppression and provides sensitivity options from 30 mA to 1000 mA with instantaneous or IDMT operation.

For a municipal submersible pump, the GA may therefore address the earth leakage element of the protection strategy.

It does not mean earth leakage is the only risk.

The same pump may also require underload, overload, phase or other motor protection depending on the application.

Phase loss and unbalance can quietly increase motor stress

Not all pump failures begin with the pump.

The electrical supply itself can create damaging operating conditions.

Three-phase motors rely on an appropriate and reasonably balanced supply. Phase loss or significant current imbalance can increase heating and place additional stress on the motor.

The problem is that a motor may continue operating under an abnormal condition before complete failure occurs.

A practical municipal motor protection strategy should therefore consider:

• Phase loss
• Current imbalance
• Overcurrent
• Undervoltage
• Overvoltage
• Short circuit
• Thermal overload

The exact requirements depend on the motor and the installation.

NewElec’s three-phase motor protection relay range allows engineers to filter relay options according to application and required protection functions rather than treating three-phase protection as a single fixed specification.

Borehole pumps need protection that reflects changing water conditions

Borehole pumps present a different risk profile from wastewater pumps.

The water may be comparatively clean, but the pump can operate far below the surface and may be difficult or expensive to retrieve if something goes wrong.

Water level can also change.

If the borehole level drops unexpectedly, the pump may experience inadequate cooling or begin operating outside its intended conditions.

Submersible borehole pumps can also be affected by sand, scale, electrical faults and damaged cable systems. The South African pump research notes reduced flow from sand or deposits, motor overheating when cooling is inadequate and electrical faults associated with control equipment and pump cabling.

This makes a borehole pump a good example of why water pump protection should consider several risks at once:

• Load loss or dry running
• Overload
• Phase conditions
• Earth leakage
• Cable and insulation condition
• Motor temperature
• Restart behaviour

Municipal teams can start with the wider NewElec pump and motor protection product range and then narrow the selection according to the actual borehole installation.

Dewatering and flood-control pumps need protection when reliability matters most

Flood-control pumps may spend long periods under relatively normal operating conditions and then suddenly be required to operate continuously during severe rainfall or flooding.

That creates a different reliability requirement.

During these periods, pump failure is particularly disruptive.

Dewatering pumps can face dirty water, suspended solids, blockage, corrosion, cable damage, dry running and overheating.

This means the protection strategy should consider more than whether the motor can be started.

It should consider whether the motor can be kept operating safely under changing conditions and whether faults can be identified quickly when a trip occurs.

NewElec’s water treatment and pump protection solutions provide a useful path into protection options for dewatering and other municipal pump applications.

The more operationally critical the pump, the more valuable good fault information becomes.

Repeated pump trips need diagnosis, not repeated resets

A pump that trips once may have experienced an isolated condition.

A pump that trips repeatedly has a pattern.

Repeated resets without understanding that pattern can hide a developing mechanical, process or electrical problem.

The useful questions are:

• Was the motor overloaded?
• Did the load disappear?
• Was there a phase problem?
• Did voltage change?
• Did the motor stall?
• Was there a blockage?
• What happened immediately before the trip?

This is where modern pump monitoring and motor protection can improve maintenance decision-making.

The NewCode Relay is one option, NewElec describes the NewCode Series as combining programmable motor protection with local and remote monitoring, overload, phase, overcurrent and earth-fault protection.

NewElec’s own training material even uses a submersible raw-water sump pump as an application example requiring overload, unbalanced-current, minimum-load and earth-leakage protection, together with visibility through a communication interface.

That is a useful illustration of how several protection requirements can exist around one pump.

Not every municipal pump needs the same relay

It is easy to move from under-protection to the opposite problem: specifying the most complex protection system for every motor.

That is not necessary either.

Municipal pump systems can be grouped according to risk and operational importance.

Standard support pumps

These may be lower-criticality pumps where dependable overload and basic motor protection are the primary requirements.

The protection should be appropriate, simple to maintain and easy for technicians to understand.

Dry-run-sensitive pumps

Borehole, sump, dewatering and some transfer pumps may need particular attention to minimum load, undercurrent or load-loss protection.

For these motors, process conditions matter as much as electrical rating.

Wet-environment or insulation-sensitive pumps

Submersible wastewater and similar installations may justify greater focus on earth leakage and insulation conditions.

NewElec’s GA Series earth leakage range can form part of the protection conversation for these circuits.

Operationally critical pumps

A major water-transfer pump or wastewater pump affecting a wider process may justify stronger diagnostics, event records and fault visibility.

For these applications, products such as the KD Series or NewCode Series may become relevant depending on the exact protection and communication requirements.

Automation-ready pump systems

Some municipal sites need more than local protection.

Where the aim is to increase remote visibility, communication or integration into broader control systems, the relay selection should include those requirements from the start.

NewElec’s Why Wait to Automate™ approach is particularly relevant to municipal sites that want to improve older motor-control infrastructure progressively rather than replace every existing system at once.

Protection should match the consequence of failure

A useful protection discussion should not only ask:

“How likely is this pump to fail?”

It should also ask:

“What happens if it does?”

The same 15 kW motor can have very different operational importance depending on the application.

One may operate a small auxiliary pump with readily available standby capacity.

Another may drive a critical transfer pump with immediate consequences for water treatment or wastewater flow.

The second motor may justify stronger monitoring, better diagnostics and more carefully coordinated protection even though the nameplate rating is identical.

This is why NewElec’s municipal motor protection solutions should be viewed through the operating role of the equipment, not only its kW rating.

It also supports more rational budgeting. Protection investment can be prioritised around assets where failure has the greatest operational consequence.

Older municipal systems can be improved in stages

A municipality does not necessarily have to replace an entire MCC to start improving pump reliability.

Many existing installations combine older panels with motors, pumps and control equipment that remain serviceable.

A more practical strategy may be to begin with:

1. Critical pumps experiencing repeated failures or trips
2. Pumps exposed to dry-running risk
3. Wet-environment applications where earth leakage is a concern
4. Motors where existing protection provides little diagnostic information
5. Pump groups where better standardisation would simplify maintenance

From there, the municipality can progressively improve protection and visibility.

This is the logic behind NewElec’s Why Wait to Automate™ approach: modernisation does not always require immediate replacement of every existing system.

Better protection can be the first step.

Better diagnostics may come next.

Communication and wider automation can follow where the operational case justifies them.

Where GA, MA, KD and NewCode fit into municipal pump protection

This should not be treated as a simple product ranking.

Different relay families solve different protection problems.

The GA Series Earth Leakage Relay is relevant where the requirement is focused earth leakage and earth fault protection, including DOL and VSD applications with harmonic suppression.

The MA Series Relay becomes relevant where load monitoring and underload detection are useful, including sump-pump applications where falling motor load can indicate that the process condition has changed.

The KD Series Relay can be considered where the application needs broader low-voltage motor protection together with fault and event information. NewElec’s current product guidance includes pumps among its target applications.

The NewCode Relay becomes relevant where a pump application requires advanced motor protection, control and supervision.

The useful question is therefore not:

“Which NewElec relay is best for municipal pumps?”

It is:

“Which protection functions does this particular pump require?”

Questions to ask before selecting municipal pump protection

Before choosing a relay or reviewing an existing municipal pump circuit, start with the pump and process.

Ask:

• What type of pump is this?
• What municipal process does it support?
• What happens if it stops?
• Can the pump run dry?
• Can the impeller become blocked?
• Does the load vary significantly during operation?
• Is the pump submerged or exposed to moisture?
• Is earth leakage protection required?
• Is the motor DOL, soft-started or VSD-driven?
• Are phase loss and voltage problems a concern?
• Do maintenance teams need to know why the motor tripped?
• Is local protection sufficient, or is communication required?
• Will the system need to support future automation?

The NewElec Relay Selection Assistant can then be used with a clearer understanding of the application, motor size and required protection functions.

That helps avoid both under-specifying protection for critical pumps and overcomplicating straightforward applications.