By Marcy de Luna

HOUSTON (Reuters). Texans are being asked to limit appliance and air conditioning use following six outage of power stations. This is a sign that there’s a flaw in the grid.

The reliability of the power grid is a concern since February last year’s freezing, when more than 200 people died in widespread blackouts. This was followed by power-price rises that led at least five power marketers to declare bankruptcy. To prevent outages in the future, Electric Reliability Council of Texas (ERCOT), is Texas’s grid operator.

The weekend power advisory did not have to do with fuel supplies, unlike outages caused by shortages or frozen generation plants. According to the state, six power plants that produce 2,900 megawatts were “tripped off”, triggering the advisory.

According to energy specialists, the resultant wholesale prices for Houston at $4,000 per megawatt-hour plus and negative prices from 150 miles (241 km) showed that power could not be purchased elsewhere.

Ramanan Krishnamoorti (chief energy officer, University of Houston) stated that a transmission problem would be able to explain why there were negative pricing and inconsistencies.

“The chances of many power plants to be offline for their own individual reasons would be infinitesimally small,” said Joshua Rhodes, a research associate at the University of Texas at Austin Energy Institute and Webber Energy Group.

ERCOT refused to provide any comment Monday and did not have a spokesperson to discuss the cause of the trippages at six generation plant. According to the operator, it will have enough power for the state in this summer.

Neal Dikeman is a partner in Energy Transition Ventures, and a former director at a smart grid firm that sells power flow control. He said congestion will likely continue to be a problem as Texas heats.

“In summer, there is often congestion caused by people turning on their air conditioners. This causes the transmission lines to tap out as the thermal limits are reached.