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Benefits of Monitoring the Electricity Going to your Pumps


admin - August 15, 2018 - 0 comments

 

Advancements in SCADA systems are impacting the water industry. The cutting-edge Internet of Things (IoT) and smart city applications are providing water operators with more information than ever before.  One such element of information is power monitoring of the electric motors that are driving your water pumps.

Simply putting in a phase monitor at the station and detecting a phase loss does not provide enough information to quickly and effectively diagnose problems at your pump stations.  Extreme Endeavors has configured our IoT hardware to include in our SCADA systems the monitoring of voltages and currents, and the benefits have paid off. 

What if we were to tell you that power monitoring could help you to detect leaks and equipment failures, and assist in preventative maintenance?  Your SCADA system should include the monitoring of voltages and currents coming into the pumps. It then logs this data to the cloud where operators, who have access to gather information about the pumps, as well as computer algorithms, automatically make decisions to keep the water production or distribution constant.

What Voltage Monitoring Can Tell Us

Monitoring the voltage that is going to your pumps tells you a lot about the quality of power that is delivered.  We have found several instances where the power company delivers voltages which are out of specification.  Each phase of voltage should be 120V RMS ± 6%, which means the lowest voltage you should read is 112.8 V RMS and the highest should be 127.2 Volts. We have found that when a power company is out of specification, it is very responsive in correcting the issue, especially if you have a graph from your SCADA system which shows the high or low voltage readings. 

However, the fault may not always be from an outside source. For example, if your voltage starts to drop, this could mean that your switchgear coming into the pump station may have loose connections or failing parts.

Likewise, failing components can be to blame. If you’re using a Variable Frequency Drive (VFD) to run your pumps and you are monitoring the voltage, this can tell you when the VFD is declining.  When the VFD starts to output erratic voltages, this is an indication that it will soon fail.

What the Current Can Tell Us

The current, or amperage, into the armature of the electric motor that drives the pump can be measured so that it informs you about the pump and the contents it is pumping. Extreme Endeavors has helped our customers to use “current” monitoring that indicates when a pump goes into cavitation and when it loses prime. We have also helped our customers to analyze the volume of water that is being pumped for leak detection applications. 

One case we would like to present was found while we were working with the Taylor County Public Service District.  One of their pump stations, the Wickwire Station, can operate as a hydrostatic station, as it did in October/November 2018 while the tank was being painted. The Wickwire Station provides water to a set of pumps that fill the Oak Grove tank.  Figure 1 shows a graph of the current draw of phase A of the electric motor that drives the pump providing the constant pressure. The blue shows the actual data, and the red line shows a running average of 20 data points.  The graph shows plateaus in the amperage, which we can correlate to the time that Oak Grove pumps are running to fill the Oak Grove tank.  It should be noted that Oak Grove pump 1 has a higher output over pump 2, hence there is less run time, as is shown in this graph. 

This graph shows a noticeable depression just after midnight. This is a time when people are using less water; hence, less current is required to supply the pump and maintain pressure. 

We can see from this example that the current measurement of a hydrostatic pump system can be used to detect leaks and system failures.  In this scenario, we could use the volume of water in the Oak Grove tank as a calibration value and determine a flow rate based on the current that is going into the motor. 

Pump current measurements also have applications that go beyond hydrostatic situations. For example, one customer uses our current monitoring system to indicate when foreign objects are stuck in the impellers of their sewage pumps.  Another customer uses current monitoring to determine when the pump goes into cavitation so that it can be shut down. 

Power Factor

Power factor is the ratio of the power that a device draws from the main supply and the power that it actually consumes, or the ratio between Real and Apparent power. A perfect power factor would be 1.0 when the device consumes all the power it draws. With a power factor of .9, 90% of the power would be consumed, while 10% is lost.  So, our goal here is to keep the power factor as close to 1.0 as possible. 

It is important to include a power factor monitoring system as part of your SCADA system because the power factor will diminish as your pumps degrade or as something changes. What many people do not realize is that they can add elements to their system which will adjust and turn the power factor close to 1.0 so that energy is used efficiently.

Conclusion

Power is a critical resource for both water distribution and production, and your SCADA system has the technology to thoroughly monitor that resource.  As with any component in your SCADA system, the benefits and features you will receive from adding this to your system are in the details, as everything from sampling rates to data processing must all be considered when you are power monitoring. 

Data processing is quickly becoming a key element in your SCADA system and is needed with power monitoring. However, a single contract, which is the normal case in most water industry installations of SCADA equipment, does not allow the optimization that is needed.  Your SCADA contract should be divided up into two phases. The first phase is design and installation. The second phase then takes place in 3 to 6 months when you develop a data processing system to add features which will give the Public Service District the most benefit.


Figure 1:  Wickwire pump station’s current draw while operating in hydrostatic mode