Evaluation Method for Real-Time Dynamic Line Ratings Based on Line Current Variation Model for Representing Forecast Error of Intermittent Renewable Generation

Abstract

Due the high penetration of intermittent renewable energy sources (IRESs), transmission line currents show large fluctuations and thus significant uncertainty. This makes it difficult to operate a power system without violating transmission capacity constraints. This paper evaluates the dynamic line ratings (DLRs) of overhead lines based on changes in the line current owing to the high penetration of intermittent renewable energy sources. In particular, by focusing on extremely large (but rare) forecasting errors in the intermittent renewable energy source output, which are generally inevitable in most forecasting methods, a model for representing the forecasting error in line with current variation due to intermittent renewable energy source output is developed. The model is based on a shape parameter that represents the equivalent current variation required for the same temperature increase as that due to the extremely large forecasting error. Finally, based on the annual minute-by-minute irradiance data, preventive control of the transmission network with dynamic line ratings is evaluated using worst-case parameter values.

A Thermal Rating Calculation Approach for Wind Power Grid-Integrated Overhead Lines

“…To exploit the transfer capability of WPIOLs, the dynamic thermal rating (DTR) technique, which calculates the thermal ratings of transmission lines based on the measured meteorological data (including ambient temperature, wind speed & direction, and solar insolation) [10,11], has been applied on WPIOLs. As reported in [12][13][14][15][16], DTR can provide a much larger thermal rating than STR in most cases, thus significantly benefitting wind power accommodation. However, compared with STR, DTR has certain disadvantages: (1) additional facilities need to be equipped to measure the weather data and transfer them to operators, adding to the cost of operation & maintenance of the power system; (2) it is not convenient for operators to use time-varying thermal ratings of transmission lines to make dispatch decisions or set the relay protections [17,18].When the overhead lines are heated in service, the annealing effect will cause conductor loss of tensile strength (LOTS).…”

“…Note that the conventional MPT is no longer used here to calculate thermal ratings; conversely, the reachable maximum operating temperature of the conductor is also decided by model (16). Moreover, the thermal rating of the WPIOL can be significantly improved by the proposed thermal rating calculation approach compared with the conventional STR under a wide variation range of the average wind speed; this further demonstrates the adaptability of the approach for the WPIOLs.…”

“…The equality constraint represents the HBE of the conductor, in which F(·) is the abbreviated expression of the heat gain and heat loss in the left side of Equation (1). Moreover, the 1st and 2nd inequality constraints represent the ground clearance constraint and cumulative LOTS constraint of the conductor, respectively; with reference to [16], the allowable LOTS was set to be 10% in this study. The 3rd inequality constraint indicates the upper bound of the decided thermal rating (I TR l ), there is no wind power curtailment when the equality holds, and the constraint can avoid the decision result of infinite thermal rating.…”

Transient Temperature Calculation and Multi-Parameter Thermal Protection of Overhead Transmission Lines Based on an Equivalent Thermal Network

“…DTLR calculation models are mostly constructed on the basis of IEEE and CIGRE standards [17,18], which simplify the heat transfer of conductor and treat the conductor as an isothermal body to obtain its surface or average temperature. Although DTLR models can reflect the electro-thermal coupling effect of transmission line under steady ambient meteorological conditions, it cannot characterize the difference in conductor inner transient temperature rise responses [19][20][21].…”

Methodologies for the Exploitation of Existing Energy Corridors. GIS Analysis and DTR Applications

“…In [11] the dynamic line ratings (DLRs) of overhead lines was evaluated based on changes in the line current owing to the high penetration of intermittent RES when large forecasting errors occur. In [12] an optimal real time transmission congestion management algorithm is proposed considering not static and fix thermal rates, but quasi-dynamic thermal rates of transmission lines.…”