S. N. Singh

A Classification Approach Using Support Vector Machines to Prevent Distance Relay Maloperation Under Power Swing and Voltage Instability

Distance relays, in the power transmission systems, are susceptible to the maloperation under certain system events, such as power swings and voltage instability, which drive the apparent impedance trajectories into the protection zones of the relay. Fast and reliable detection of the symmetrical faults, occurring during power swings, poses another challenge to operation of the distance relays. This paper introduces a new classification and protection scheme based on support vector machines (SVMs) for offering supervisory control to the operation of the conventional distance relays. The proposed scheme segregates the power system events into faults, power swings, and voltage instability. This paper also proposes a new index, called the relay ranking index, for identifying the relays most vulnerable to the maloperation due to power swings and voltage instability. The proposed SVM classifiers can work in unison with the conventional distance relay unit. The performance of the proposed scheme has been tested on a nine-bus WSCC system and 39-bus New England system.

Analysis of Notch and TGF- β Signaling Expression in Different Stages of Disease Progression During Hepatitis B Virus Infection

OBJECTIVES:CD4+ regulatory T cells (Tregs) seem to have a key role in persistence of hepatitis B virus (HBV) infection. Notch and transforming growth factor (TGF-β) signaling independently help in the differentiation and regulation of CD4+T cells, including T-helper (TH) 1, TH2, and Tregs. Whether, the two pathways have modulatory role on different stages of HBV infection and severity of liver disease is not clear. We investigated Notch and TGF-β families’ gene expression in peripheral blood and intrahepatic lymphocytes in patients with different stages of chronic HBV (CHB) infection.METHODS:Peripheral blood mononuclear cells (PBMCs), CD4+, and CD8+ T cells were isolated from patients with acute HBV (AVH-B, n=15), CHB (n=16), and controls (HC, n=10). In addition to PBMCs, intrahepatic lymphocytes were obtained from liver biopsies from CHB (n=12), cirrhosis (n=12), hepatocellular carcinoma (HCC, n=5), and healthy livers (n=5). Notch family (Notch1–4, Hes1, Jag1, and NF-kβ) and TGF-β family gene expressions were studied by real-time PCR, flow cytometry, and immunohistochemistry.RESULTS:Relative expression of Notch signaling target genes, Hes1 and NF-kβ, was higher in the total PBMCs of AVH-B and CHB patients than that in HC patients (Log relative quantification (RQ); 1.1 AVH-B vs. 0.3 HC, 1.3 CHB vs. 0.3 HC; P=0.02). CD8+ T cells showed upregulated expression of Hes1 and Notch1 (P=0.02 and 0.01, respectively) in AVH-B than in CHB patients. Also, in AVH-B patients, HBV-specific CD8+ T-cell proliferation (5.74% vs. 2.7%) and TGF-β signaling activity were higher. All Notch receptors and ligands were upregulated in the PBMCs in CHB infection (CHB vs. cirrhosis, P=0.001; CHB vs. HCC, P=0.023; and cirrhosis vs. HCC, P=NS). Intrahepatic expression of Notch1 and FoxP3 were significantly higher in cirrhotics and HCCs, and further blockage of Notch signaling reduced the FoxP3 expression. Array data of TGF-β family showed increased TGF-β3, TGF-α, SMAD3, SMAD4, SMAD6, and GDF9 expression on intrahepatic lymphocytes in cirrhotic and HCC patients compared with CHB.CONCLUSIONS:Our findings suggest that there is a complementary association between Notch1 and Hes1 in CD8+T cells during AVH-B infection. On development of CHB infection, repression of the Notch receptors mediates the regulation of immune response in patients, who progress to cirrhosis and HCC. Finally, HBV infection drives increased Notch1, TGF-β, and FoxP3 expression on intrahepatic T cells in cirrhosis, resulting in fibrogenesis and disease progression.

WAMS assisted frequency and voltage stability based adaptive load shedding scheme

A power system, operating close to its power transfer limit, may experience frequency as well as voltage instability on occurrence of a critical contingency. This paper proposes a two-step adaptive load shedding strategy, simultaneously addressing the frequency and the voltage instabilities through estimation of magnitude of the disturbance and evaluation of the stability margins. In the first step, disturbance power is calculated, assuming the availability of the real-time data from Wide Area Measurement System (WAMS). This is compared with a threshold value of power mismatch, derived using a low order System Frequency Response (SFR) model, to judge the severity of the disturbance. Optimal locations and magnitude of the load curtailments have been decided according to a dynamic voltage stability index, computed at each load bus. The second step of the proposed scheme determines the optimal re-dispatching of generators to ensure minimal load curtailments for the post disturbance operating condition. Performance of the proposed scheme is tested on New England 39-bus system.

Electrical load profile analysis and peak load assessment using clustering technique

Load profile analysis in different regions is very useful to power utilities for managing the load requirements in economic and efficient manner. For the demand side management and grid operation, the variation in demand is to be known. In this paper, classical k-means clustering approach is used for finding similar types of profiles of a practical system for demand variation analysis and energy loss estimation. For different zones, typical load profiles based on similar consumption are obtained. Primarily, the load factor represents feeder demand variation, and loss factor helps average energy loss estimation in distribution power system without load flow studies. In this paper, a concept is proposed for analysis of electricity consumption pattern on different days in particular zones based on cluster load factor and cluster loss factor. Normal and abnormal peak load requirements in cluster of similar types of profile of days of different zones are identified. Cluster loss factor helps in identifying the energy loss variation due to different load patterns.

Critical load profile estimation for sizing of battery storage system

This paper proposes a method to find the critical load profile for estimating the battery storage size. The critical load profile consists of broadest peak in annual historical load profile data and is assumed an outlier. The local outlier factor approach is implemented in finding the outliers, which are ranked according to degree of anomalies. The discharge duration in critical load profile, with consideration of percentage load growth in peak load of base year and maximum allowed demand 8.5 MW at IIT Kanpur, helps in deciding the expected size of Battery Energy Storage System (BESS). The BESS sized with this power and energy ratings is useful in daily time deferrals, load leveling and peak shaving applications.

An improved phasor assisted state estimator

Conventionally, state estimation programs are being run at an interval of 3–5 minutes in modern energy management systems. The Wide Area Monitoring System (WAMS), utilizing synchro-phasor data, offers a great promise in improving the system state estimation. The phasors can be acquired and refreshed at every 20–50ms. This paper presents a new method to obtain a more accurate and faster method for power system state estimation. The accuracy has been improved by using phasor measurements along with Supervisory Control and Data Acquisition (SCADA) measurements in the traditional Weighted Least Square (WLS) state estimator. Faster convergence has been achieved by using phasor measurements which are available between the two consecutive state estimation runs. The effectiveness of the proposed method has been established on three test systems, viz. the IEEE 14-bus system, New England (NE) 39-bus system and Northern Region Power Grid (NRPG) 246-bus Indian system.

Demand side management system for future buildings

This paper proposes a new demand-side management (DSM) scheme for autonomous DC microgrid for the future building. The DC distribution system is considered as a prospective system due to the increase of DC loads and DC power sources such as photovoltaic (PV), and battery bank (BB). The BB responds to the changes in power imbalance between PV generation and demand within an autonomous DC microgrid. The power loss during charging/discharging in the battery is the great challenge for the autonomous DC microgrid supplied by PV. It decreases the system efficiency. The control objective of the proposed DSM scheme is to use the PV energy more efficiently. The proposed control algorithm shifts the deferrable load from non-sunny hours to sunny hours and decreases the building demand during non-sunny hours. In this way it decreases the charging/discharging cycles of the batteries. This is reducing the power losses in the battery and improves system efficiency. The proposed scheme reduces the size of the PV plant, storage and capital cost of the system.