Electrical Power Quality

Transkript

1 ELE 789 Special Topics in Electrical and Electronics Engineering: Electrical Power Quality Dr. H.Bilge Mutluer 1

2 Course Outline 1. Power Quality (PQ) Definitions and Objectives 2. Power System Modeling and Simulation for PQ Analyses 3. Voltage Quality 4. Harmonics and Harmonic Elimination 5. Reactive Power Compensation 6. EMI, Grounding and Wiring 2 Outline 2

3 Power System Modeling and Simulation for PQ Analyses Modeling tools MATLAB and SIMULINK EMTDC / PSCAD Other Tools Simulation types Investigation of the Power System Identification of Parameters Load Identification and Definition of the Problem PQ Monitoring Sample Study in PSCAD 3 3

4 The Role of Simulation in Design Electrical Power Systems: Electrical circuits Electromechanical devices (motors, generators, etc ) Performance should increase Traditional tools and techniques Nonlinearities High Power and Power Electronics applications 4 The Role of Simulation in Design (MATLAB) Electrical power systems are combinations of electrical circuits and electromechanical devices like motors and generators. Engineers working in this discipline are constantly improving the performance of the systems. Requirements for drastically increased efficiency have forced power system designers to use power electronic devices and sophisticated control system concepts that tax traditional analysis tools and techniques. Further complicating the analyst's role is the fact that the system is often so nonlinear that the only way to understand it is through simulation. Land-based power generation from hydroelectric, steam, or other devices is not the only use of power systems. A common attribute of these systems is their use of power electronics and control systems to achieve their performance objectives. 4

5 Simulation Tools Reduced Scale Models Analog Models Digital Models Hybrid Models Equivalent Models 5 Power System Simulation Jean-Paul Barret, Pierre Bornard, B. Meyer 5

6 Computer Programs Used for Power Quality Analysis and Simulation MATLAB and Simulink EMTDC / PSCAD PSS/E, PSS-SINCAL P-Spice (ORCAD) Others 6 Power system simulation (Wikipedia) models are a class of computer simulation programs that focus on the operation of electrical power systems. These computer programs are used in a wide range of planning and operational situations including: -Long-term generation and transmission expansion planning -Short-term operational simulations -Market analysis (e.g. price forecasting) 6

7 MATLAB MATLAB is a high-performance language for technical computing. integrates computation, visualization, programming Solutions are expressed in familiar mathematical notation. 7 7

8 MATLAB MATLAB Development environment The MATLAB Mathematical Function Library The MATLAB Language Graphics The MATLAB Application Program Interface (API) 8 8

9 MATLAB Interface 9 9

10 Simulink Simulink is an environment for multidomain simulation and Model-Based Design for dynamic and embedded systems. Provides an interactive graphical environment and a customizable set of block libraries that let you design, simulate, implement, and test a variety of time-varying systems 10 Simulink is integrated with MATLAB, providing immediate access to an extensive range of tools that let you develop algorithms, analyze and visualize simulations, create batch processing scripts, customize the modeling environment, and define signal, parameter, and test data. Key Features Extensive and expandable libraries of predefined blocks Interactive graphical editor for assembling and managing intuitive block diagrams Ability to manage complex designs by segmenting models into hierarchies of design components Model Explorer to navigate, create, configure, and search all signals, parameters, properties, and generated code associated with your model Application programming interfaces (APIs) that let you connect with other simulation programs and incorporate hand-written code Embedded MATLAB Function blocks for bringing MATLAB algorithms into Simulink and embedded system implementations Simulation modes (Normal, Accelerator, and Rapid Accelerator) for running simulations interpretively or at compiled C-code speeds using fixed- or variable-step solvers Graphical debugger and profiler to examine simulation results and then diagnose performance and unexpected behavior in your design Full access to MATLAB for analyzing and visualizing results, customizing the modeling environment, and defining signal, parameter, and test data Model analysis and diagnostics tools to ensure model consistency and identify modeling errors 10

11 Simulink 11 11

12 Fixed Step Solvers Simulink provides two distinct types of fixed-step continuous solvers: explicit and implicit solvers. Explicit: İmplicit solver: where X is the state, DX is the state derivative, and h is the step size

13 Fixed Step Solvers 13 13

14 ODE 1 Recall Jacobian Matrix: 14 14

15 Solver ode45 ode23 ode113 Ode 15s ode23s ode23t ode23tb Variable Step Solvers Method Explicit Runge- Kutta, Dormand-Prince pair Explicit Runge- Kutta Bogacki and Shampine pair multistep solver variable-order solver numerical differentiation formulas (NDF) Rosenbrock formula of order 2 trapezoidal rule using a "free" interpolant implicit Runge-Kutta formula with a first stage Advantages / Usage For continuous state More efficient than ode45 at stringent tolerances needs the solutions at several preceding time points problem is stiff, or if ode45 failed or was very inefficient stiff problems for which ode15s is not effective solution without numerical damping can be more efficient than ode15s at crude tolerances 15 Simulink provides the following variable-step continuous solvers: - ode45 is based on an explicit Runge-Kutta (4,5) formula, the Dormand-Prince pair. It is a onestep solver; that is, in computing y(tn), it needs only the solution at the immediately preceding time point, y(tn-1). In general, ode45 is the best solver to apply as a first try for most problems. For this reason, ode45 is the default solver used by Simulink for models with continuous states. - ode23 is also based on an explicit Runge-Kutta (2,3) pair of Bogacki and Shampine. It can be more efficient than ode45 at crude tolerances and in the presence of mild stiffness. ode23 is a one-step solver. ode113 is a variable-order Adams-Bashforth-Moulton PECE solver. It can be more efficient than ode45 at stringent tolerances. - ode113 is a multistep solver; that is, it normally needs the solutions at several preceding time points to compute the current solution. - ode15s is a variable-order solver based on the numerical differentiation formulas (NDFs). These are related to but are more efficient than the backward differentiation formulas, BDFs (also known as Gear's method). Like ode113, ode15s is a multistep method solver. If you suspect that a problem is stiff, or if ode45 failed or was very inefficient, try ode15s. - ode23s is based on a modified Rosenbrock formula of order 2. Because it is a one-step solver, it can be more efficient than ode15s at crude tolerances. It can solve some kinds of stiff problems for which ode15s is not effective. - ode23t is an implementation of the trapezoidal rule using a "free" interpolant. Use this solver if the problem is only moderately stiff and you need a solution without numerical damping. - ode23tb is an implementation of TR-BDF2, an implicit Runge-Kutta formula with a first stage that is a trapezoidal rule step and a second stage that is a backward differentiation formula of order two. By construction, the same iteration matrix is used in evaluating both stages. Like ode23s, this solver can be more efficient than ode15s at crude tolerances. 15

16 Variable Step Solvers Compute local and estimated error for states If greater than expected, reduce time step, compute again 16 Specifying Variable-Step Solver Error Tolerances: The solvers use standard local error control techniques to monitor the error at each time step. During each time step, the solvers compute the state values at the end of the step and also determine the local error, the estimated error of these state values. They then compare the local error to the acceptable error, which is a function of the relative tolerance (rtol) and absolute tolerance (atol). If the error is greater than the acceptable error for any state, the solver reduces the step size and tries again: Relative tolerance measures the error relative to the size of each state. The relative tolerance represents a percentage of the state's value. The default, 1e-3, means that the computed state is accurate to within 0.1%. Absolute tolerance is a threshold error value. This tolerance represents the acceptable error as the value of the measured state approaches zero. The error for the ith state, ei, is required to satisfy: e i <=max(rtol x x i, atol i ) 16

17 Simulink Power GUI allows you to choose one of three methods to solve your circuit Perform several operations 17 What the Powergui Block DoesThe Powergui block allows you to choose one of three methods to solve your circuit: Continuous method, which uses a variable step solver from Simulink Discretization of the electrical system for a solution at fixed time steps Phasor solution method The Powergui block also allows you to Display steady-state values of measured current and voltages as well as all state variables (inductor currents and capacitor voltages) in a circuit. Modify the initial states in order to start the simulation from any initial conditions. The names of the state variables are the name of the block where the capacitor or the inductor is found, preceded by the Uc_ label for capacitor voltages and by the IL_ label for the inductor currents. Perform load flows and initialize three-phase networks containing three-phase machines so that the simulation starts in steady state. This option is available with circuits containing the following types of machines: Simplified Synchronous Machine, Synchronous Machine, or Asynchronous Machine (squirrel cage) blocks. Display impedance versus frequency plots when Impedance Measurement blocks are present in your circuit. Perform FFT analysis of the simulation results. Generate the state-space model (SS) of your system (if you have the Control System Toolbox installed) and automatically open the LTI Viewer interface for time and frequency domain responses. Generate a report containing steady-state values of the measurement blocks, the sources, the nonlinear models, and the states of your circuit. The report is saved in a file with the.rep extension. Model the hysteresis characteristic of the Saturable Transformer blocks. 17

18 EMTDC/PSCAD Introduction Fundamentals of EMTDC and PSCAD PSCAD Interface Sample Circuits Using Menus and Accessories Building Blocks Program Execution 18 18

19 What is EMTDC Electro-Magnetic Transients in DC systems Professional's simulation tool for analyzing power systems. EMTDC is the simulation engine E Executes the fortran programmes generated by PSCAD

20 What is PSCAD Power Systems Computer Aided Design User interface for EMTDC program. PSCAD/EMTDC is most suitable for simulating thetime domain instantaneous responses, also popularly known as electromagnetic transients of electrical systems

21 Fortran Compilers TCP/IP Licence Manager Control License Manager Installation 21 21

22 EMTDC Simulation Loop Fixed time step Background operations Executes EMTDC time step (in us) 22 22

23 The purpose of the main program Read data defining electric circuit parameters Assemble electrical networks Interface a users model assembled in subroutine DSDYN Computed output quantity is formulated or processed by modelling statements into an array each time step and printed into output DSDYN can be frozen in time for future use in a "SNAPSHOT" file. Multiple reruns can also be automatically initiated to search for an optimum value of a parameter. 23 DSDYN : User defined dynamics DSOUT -- User defined output 23

24 Generalized Branches 24 24

25 Capacitor Modelling 25 The theoretical basis of the solution method is similar to that described in Dommel's classic paper Delta t : = time interval between successive calculations or time step 25

26 Inductor Modelling 26 The theoretical basis of the solution method is similar to that described in Dommel's classic paper Delta t : = time interval between successive calculations or time step 26

27 A Sample Circuit 27 27

28 Solution of the Circuit At node 1, At node 2, These equations are reduced to their matrix form as follows: 28 28

29 and in short form, Solution of the Circuit and the solution to the node voltages defined by column matrix [V] is: EMTDC does not actually form the inverse of the G matrix. It actually solves equation [1.10] using forward triangularization and back-substitution. This method takes advantage of the sparse nature of the G matrix

30 30 30

31 31 31

32 PSCAD Interface Title & Menu Bar Project Tree Components Channels Message Tree Plot 32 32

33 Using Master Library 33 33

34 Case Properties 34 34

35 Using Menus 35 35

36 Workspace Menus 36 36

37 Component Menus

38 Assembling the Components 38 38

39 Assembling the Components 39 39

40 Nodes & Signals Nodes correspond to electrical network Signals correspond to: control parameters (can be analog or digital) acquired data by measuring the node voltages or currents. Signals and nodes can not be named the same or connected directly to each other PA Eab PB PB Ebc PC PC Eca PA Eab Ebc Eca 40 40

41 Using Node Labels Effectively BRKc SPA1 A 1.0 TIME SPB1 B 1.0 deblock fp1 fp1 SPC1 C 1.0 Eab Ebc Eca V1 V2 V3 Firing Pulse Generator fp2 fp3 fp4 fp5 fp2 fp3 fp4 fp5 Ists1 Ists2 Ists3 PA PB PC PA Eab PB PB Ebc PC PC Eca PA delay1delay2delay3 fp6 fp6 Firing angle can be set if this control is 0 Iss1 PA Iss2 PB Iss3 PC 5th and 7th Harmonic Filters 41 41

42 Channels and Plots Channels are connected to signals for creating plot. Plots, graphs and curves are special PSCAD objects designed to interactively display EMTDC data, both during a run and when a run is complete qp1 qp2 qp3 Qtot QSPLY 42 42

43 Plots, Graphs and Curves 43 43

44 Control Panels A control panel is a special built-in component for holding slider, switch, push button, dial, and meter interfaces. These interfaces can reside only inside a control panel

45 Control Panels V_lev f_lev autoref * dlyman autoref

46 Program Execution 46 46

47 Case Properties 47 47

48 Topics on PSCAD Designing Components Editing Designs Creating Instances Real Time Simulation Mitigating Known Problems 48 48

49 Investigation of Power System 49

50 Load Identification (a) 50 50

51 Load Identification Data Acquisition system NI DAQCard 6062E, SC-2040 S/H Card (0.5 Ms/s) 51 51

52 Load Identification Single line diagram Monthly electric bills Daily active and reactive power demands Detailed information about electric motor drives, transformers An investigation of previously installed shunt compensators, and capacitors Future production plans and machine stocks 52 52

53 POWER QUALITY MEASUREMENT DEVICES HARMONIC ANALYZERS TRANSIENT-DISTURBANCE ANALYZERS OSCILLOSCOPES DATA LOGGERS AND CHART RECORDERS TRUE RMS METERS 53 53

54 POWER QUALITY MEASUREMENT Number of Test Location Standards (i.e. IEEE , IEC , ve ) Test Duration Test Method Devices Safety 54 54

55 Sample Case Study, PQ Monitoring MOBİL L GÜÇG KALİTES TESİ ÖLÇÜMLERİ ALT PROJESİ 55

56 Mobil GüçG Kalitesi Ölçüm m Sisteminde Kullanılan lan Ekipmanlar Alet Çantası ve El Tipi Ölçü Aleti Akım Probu DAQ Kart SC2040 Kart Mobil Şarj Aküsü 56 56

57 Mobil GüçG Kalitesi Ölçüm m Sistemi Genel GörünümüG Ölçüm m Bilgisayarları,, SC2040 Kartlar ve Ölçüm m Sehpası 57 57

58 Ölçümler MOBİL ÖLÇÜM YAZILIMI - IEEE , IEC , ve standartlarına uygun veri toplanması ve gerçek zamanlı analizi - 7 Gün kesintisiz ölçüm - 3 Faz Gerilim, 3 Faz Akım olmak üzere 6 kanal veri toplanması - Kanal Başına Örnekleme Hızı:3200 Örnek/Saniye (Çevrim Başına 64 Örnek Alma) 58 58

59 MOBİL ÖLÇÜM M YAZILIMI VERİ KAYIT ŞEKLİ - Gerilim ve Akım RMS Değerleri:10 Çevrimlik Ortalamalar - Aktif Güç, Reaktif Güç, Görünen Güç ve Güç faktörü : 1 Saniyelik Ortalamalar - Akım ve Gerilim Harmonikleri : 3 Saniyelik Ortalamalar - Gerilim Kırpışması(Fliker) : P st (Kısa Dönem Fliker Şiddeti):10 Dakikalık Ortalamalar P lt (Uzun Dönem Fliker Şiddeti): 2 Saatlik Ortalamalar - Gerilimde Meydana Gelen Olaylar: Çevrim Başına 64 Örnek 59 59

60 Mobil GüçG Kalitesi Ölçüm m Araçlar ları 60 60

61 Mobil Ölçüm m Sistemleri TM Kumanda Odası İçindeki Ölçüm Sistemleri 61 61

62 MOBİL ÖLÇÜM M MERKEZLERİ MOBİL ÖLÇÜM M PROGRAMINA DAHİL L EDİLEN 161 MERKEZ 62 62

63 ÖLÇÜM M YAPILAN MERKEZLER 74; 46% 87; 54% Ölçüm Yapılan Merkezler Ölçüm Yapılacak Merkezler 63 63

64 AKIM HARMONİKLER KLERİ RAPORLANAN ÖLÇÜM NOKTALARINDAKİ TDD PROBLEMİ YÜZDESİ 24; 45% 29; 55% TDD PROBLEMİ VAR TDD PROBLEMİ YOK 64 64

65 GERİLİM M HARMONİKLER KLERİ RAPORLANAN ÖLÇÜM NOKTALARINDAKİ THD PROBLEMİ YÜZDESİ 16; 30% 37; 70% THD PROBLEMİ VAR THD PROBLEMİ YOK 65 65

66 UZUN DÖNEM D FLİKER ŞİDDET DDETİ (Plt)- 380 kv 380 kv Gerilim Seviyesinde Uzun Dönem Fliker Şiddeti RAPORLANAN ÖLÇÜM NOKTALARINDAKİ FLİKER PROBLEMİ YÜZDESİ Trafo Merkezi Sınır Değeri (0,65) Aşma Yüzdesi İçdaş(Karabiga) 97,6% Aliağa 93,8% Işıklar 12,1% Uzundere 6,5% Varsak 4,8% 4; 50% FLIKER PROBLEMİ VAR FLIKER PROBLEMİ YOK 4; 50% 66 66

67 UZUN DÖNEM D FLİKER ŞİDDET DDETİ (Plt)- 154 RAPORLANAN kv ÖLÇÜM NOKTALARIND Sınır Değeri(0,72) Aşma Yüzdesi AKİ FLİKER 16; 42% PROBLEMİ YÜZDESİ 22; 58% 154 kv Gerilim Seviyesinde Uzun Dönem Fliker Şiddeti Trafo Merkezi Aliağa 100,0% Almak 98,8% Alçuk 98,8% Habaş 98,7% İçdaş(İstanbul) 94,6% Alaçatı 45,8% Akçansa 19,6% Aydın 10,8% Çorlu 8,7% Alanya 7,2% Varsak 4,8% Çananakkale Çimento 3,3% Bares 2,4% Narlı 1,2% FlLIKER PROBLEMİ VAR FLIKER PROBLEMİ YOK 67 67

68 UZUN DÖNEM D FLİKER ŞİDDET DDETİ (Plt)- 33 kv 33 kv Gerilim Seviyesinde Uzun Dönem Fliker Şiddeti Trafo Merkezi Sınır Değeri(0,85) Aşma Yüzdesi İçdaş(İstanbul) 100,0% Kaptançelik 100,0% Almak 98,8% Alçuk 98,8% Habaş 98,8% Karabiga 95,0% Bores 38,0% Gebze 16,3% Alaçatı 13,6% Kumlimanı 12,0% Alanya 10,8% Bares 9,6% Botaş 4,9% Demirer 4,8% Çanakkale Çimento 3,5% RAPORLANAN ÖLÇÜM NOKTALARINDAKİ FLİKER PROBLEMİ YÜZDESİ 13; 31% 29; 69% FlLIKER PROBLEMİ VAR FLIKER PROBLEMİ YOK 68 68

69 OLAY LİSTESL STESİ 69 69

70 %Endüktif Reaktif/ Aktif Oranı 50; 50% 50; 50% %20 Sınırı Aşan %20 Sınırını Aşmayan 70 70

71 %Kapasitif Reaktif/ Aktif Oranı 3; 5% 60; 95% %15 Sınırı Aşan %15 Sınırını Aşmayan 71 71

72 KAPTANÇEL ELİK K TRAFO MERKEZİ ÖLÇÜM M RAPORU ÖZET TABLOSU 72 72

73 YÖNETMELİKLER ÜLKEMİZDE GÜÇ KALİTESİNİ BELİRLEYEN YÖNETMELİKLER Elektrik İletim Sistemi Arz Güvenilirliği ve Kalitesi Yönetmeliği ( Tarih sayılı Resmi Gazetede yayımlanmıştır.) - Sistem İşletme Gerilim Sınırları - Akım Harmonik Limitleri - Endüktif /Aktif Enerji Oranı ve Kapasitif /Aktif Enerji Oranı Limitleri Elektrik Piyasası Şebeke Yönetmeliği ( Tarih sayılı Resmi Gazetede Yayımlanmıştır.) - Gerilim Harmonik Limitleri - Gerilim Kırpışması(Fliker) Şiddetleri Limitleri 73 73

74 Sistem İşletme Gerilim SınırlarS rları 74 74

75 AKIM HARMONİK LİMİTLERİ 75 75

76 GERİLİM HARMONİK LİMİTLERİ 76 76

77 ENDÜKTİF/AKTİF ve KAPASİTİF/AKTİF ENERJİ ORANLARI LİMİTLERİ Doğrudan Bağlı Müşteriler Dağıtım Şirketleri (%) Endüktif Kapasitif (%) Endüktif Kapasitif 0 Ocak 2007 Ocak 2008 Ocak Ocak 2007 Ocak 2008 Ocak Ocak 2007 tarihli ve sayılı Resmi Gazetede yayımlanan değişiklikle yürürlüğe giren yeni değerleri ve oranları göstermektedir

78 Örnek Ölçümler 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI GERİLİM (GERÇEK-RMS) DEĞİŞİMLERİ Faz-Faz Gerilim Gerçek-RMS Değişimi (5 dakikalık ortalamalar şeklinde) 78 78

79 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI GERİLİMDE ve AKIMDA MEYDANA GELEN OLAYLAR Gerilim Çukuru (Voltage Sag) Olay Süresince Hat Akımları Değişimi Başlangıç Tarihi: saat: 19:30:51 Bitiş Tarihi: saat: 19:30:

80 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI Gerilim Tepesi (Voltage Swell) Olay Süresince Hat Akımları Değişimi Başlangıç Tarihi: saat: 13:15:04 Bitiş Tarihi: saat: 13:15:

81 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI AKTİF, REAKTİF, GÖRÜNEN GÜÇLER ve GÜÇ FAKTÖRÜ DEĞİŞİMLERİ Aktif Güç, Reaktif Güç ve Görünen Güç Değişimleri (10 dakikalık ortalamalar şeklinde) Güç Faktörü Değişimi (10 dakikalık ortalamalar şeklinde) 81 81

82 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI AKIM HARMONİKLERİ DEĞİŞİMLERİ Hat Akımı 2. Harmonik Bileşeni (3 saniyelik ortalamalar şeklinde) Ölçülen Yapılan TM lerde en baskın harmonik olarak dikkat çekmektedir. Hat Akımı 4. Harmonik Bileşeni (3 saniyelik ortalamalar şeklinde) 82 82

83 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI Hat Akımı 6. Harmonik Bileşeni Hat Akımı 3., 5., 7. ve 9. Harmonik Bileşenleri Hat Akımı 8. Harmonik Bileşeni Hat Akımı Toplam Talep Bozulumu (TDD) 83 83

84 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI GERİLİM HARMONİKLERİ DEĞİŞİMLERİ Fazlar Arası Gerilim 2., 11. ve 13. Harmonik Bileşenleri (3 saniyelik ortalamalar şeklinde) Fazlar Arası Gerilim 3., 5. ve 7. Harmonik Bileşenleri (3 saniyelik ortalamalar şeklinde) 84 84

85 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI Fazlar Arası Gerilim 4.Harmonik Bileşeni Fazlar Arası Gerilim 8. ve 10.Harmonik Bileşenleri Fazlar Arası Gerilim Fazlar Arası Gerilim Toplam Harmonik Bozulumu (THD) 6., 23. ve 25. Harmonik Bileşenleri 85 85

86 34.5 kv İZÇELİK-1 FİDERİ ÖLÇÜM SONUÇLARI GERİLİM KIRPIŞMASI (FLİKER) P st (Kısa Dönem Fliker) Değişimi (10 dakikalık ortalamalar şeklinde) P lt (Uzun Dönem Fliker) Değişimi (2 saatlik ortalamalar şeklinde) 86 86

87 154/34.5 kv TRAFO-A PRİMER TARAFI ÖLÇÜM SONUÇLARI GERİLİM (GERÇEK-RMS) DEĞİŞİMLERİ Faz-Faz Gerilim Gerçek-RMS Değişimi (5 dakikalık ortalamalar şeklinde) 87 87

88 154/34.5 kv TRAFO-A PRİMER TARAFI ÖLÇÜM SONUÇLARI GERİLİMDE ve AKIMDA MEYDANA GELEN OLAYLAR Gerilim Dengesizliği (Voltage Unbalance) Olay Süresince Primer Akımları Değişimi Başlangıç Tarihi saat: 04 :14:58 Bitiş Tarihi: saat: 04 :14: