Surge, Lighting Protection Keeps Water Flowing
A few years ago, the San Jacinto River Authority/Woodlands Division experienced significant downtime in its well motors due to lightning events and transient surges resulting in motor failures.
A few years ago, the San Jacinto River Authority/Woodlands Division experienced significant downtime in its well motors due to lightning events and transient surges resulting in motor failures. These wells, most of which have 200 hp, 480v vertical hollow-shaft motors, are needed to meet the high water demand of the authority's customers, especially during the hot summer months.
The San Jacinto River Authority (SJRA) is an agency of the State of Texas created in 1937 by special acts of the Texas Legislature. Its purpose is to develop, conserve and protect water resources of the San Jacinto River Basin. The SJRA is responsible for a number of activities, which include municipal and industrial water supply, water quality management, wastewater treatment and water and soil conservation.
SJRA installed Combotrab, a series of lightning arrestor and transient voltage surge suppression (TVSS) combined solutions, at select well sites.
The authority operates three divisions: Woodlands, Lake Conroe Dam, and Highlands. The Woodlands division, located in southern Montgomery County, provides water supply and wastewater treatment services from centralized facilities to the 60,000-member community. To provide these services, the SJRA operates three wastewater treatment facilities with numerous pump stations, 28 water wells, elevated water storage tanks, and distribution facilities. The Woodlands division also sells water wholesale to the local Municipal Utility Districts.
A local repair shop evaluated the damaged motors and estimated repairs would be between $3000 and $8000 (on rebuildable motors) and indicated the failures observed were the result of lightning strike/transient surge events. Each time a motor failed, it cost SJRA money in repairs and put a strain on the remaining wells.
"It's a critical application and it's our job to provide continuous service to our customers," said Riley Johnson, Maintenance Manager for SJRA/ Woodlands Division.
To find out why this was becoming a frequent occurrence, SJRA contracted Shrader Engineering, (Houston, TX) an Electrical/Instrumentation firm, to conduct site surveys and propose solutions.
After reviewing the downtime causes, Roy Lackey, Technical Services Manager at Shrader, recommended implementing lightning and surge protection from Phoenix Contact Inc. (Harrisburg, PA) and improving grounding techniques to eliminate this cause of failures. The recommendation was necessary due to the well sites being located within an area that annually records an average of six lightning events per square kilometer.
"Water well casings are the best ground rods in this area," Lackey said. "In order to protect a well motor it is necessary to remove enough of this lightning, or surge energy, from the motor conductors and divert it to a ground path ahead of the well casing. This must be accomplished with a product that reacts extremely fast and is robust in construction to be there for the next event."
SJRA installed Combotrab, a series of lightning arrestor and transient voltage surge suppression (TVSS) combined solutions, at select well sites. Combotrab is comprised of a Flashtrab Plus Ctrl lightning arrestor. The Flashtrab technology is tested to the 10 x 350 mS waveform, which is the only standardized direct strike lightning test (IEC 61024). The technology handles the current associated with a direct or close lightning hit, while providing clamping voltages under 900V independent of surge current.
The Combotrab combines this lightning energy handling technology with a tightly coordinated TVSS component, to address both lightning events and switching type transients effectively, providing Category C and B protection in one fully enclosed unit. This makes many downstream TVSS devices unnecessary.
SJRA had used surge protection devices (SPDs), but learn the SPDs installed were not "true" lightning/surge protection devices and were not installed correctly. The original SPDs selected, coupled with the installation techniques used, led to the motor failures.
"The critical point to any protection application, such as this, is proper equipment selection and in the installation, minimizing cable length and any cable bends," said Lackey. "Minimal ground rod impedance and proximity to the Combotrab device is also crucial for optimum protection."
Most of the Woodlands Division well pumps have 200 hp, 480v vertical hollow-shaft motors.
Prior to installing the system, SJRA was losing approximately four motors a year. Since the installation of the new protection system on selected motors, approximately 11/2 years ago, the authority has had only one motor failure.
"The damage was very minor and the motor shop indicated it may have been a mechanical issue, because the surge protection was doing its job," Johnson said.
The reduction in failures has enabled SJRA to increase uptime and revenue in the supply of water to its customers while reducing equipment expenses.
SJRA has standardized on Phoenix Contact equipment on all new installations as well as future upgrades and retrofits. The agency currently has 10 well motors protected by Combotrab and is using other Phoenix Contact surge protection products to protect critical instrumentation and communication lines.